Implants

ABSTRACT

An implantable prosthesis including at least one element defining a bone-engaging surface, the bone-engaging surface including an anchoring mechanism operative for enhancing anchoring and adhesion of the joint defining element to the bone and thus improving the stability and longevity of the prosthesis.

REFERENCE TO RELATED APPLICATIONS

This application is partially based upon and claims priority from:

U.S. Provisional Patent Application Ser. No. 60/383,483 filed May 23,2002 and entitled “JOINT IMPLANTS SYSTEM AND METHODOLOGY AND IMPLANTSAND TOOLS USEFUL THEREWITH”; and PCT Patent Application Serial No.PCT/IL02/00972 filed on Dec. 3, 2002 and entitled: “CUSHION BEARINGIMPLANTS FOR LOAD BEARING APPLICATIONS”; and PCT Patent ApplicationSerial No. PCT/IL03/00063.A filed on Jan. 24, 2003 and entitled: “JOINTPROSTHESIS”

FIELD OF THE INVENTION

The present invention relates generally to implants and methods relatingthereto.

BACKGROUND OF THE INVENTION

The following patents are believed to be relevant to the subject matterof this application:

U.S. Pat. Nos. 5,201,881; 5,011,497; 4,279,041; 5,080,675; 4,650,491;3,938,198; 4,292,695; 4,624,674; 2,765,787; 4.735,625; 5,370,699;5,641,323; 5,323,765; 5,658,345; 3,875,594; 3,938,198; 4,292,695;4,344,193; 4,570,270; 4,650,491; 4,279,041; 4,661,112; 4,662,889;4,664,668; 4,715,859; 4,795,470; 4,795,474; 4,808,186; 4,813,962;4,822,365; 4,888,020; 4,904,269; 4,908,035; 4,919,674; 4,919,678;4,936,856; 4,938,771; 4,938,773; 4,950,298; 4,955,912; 4,955,919;4,963,153; 4,963,154; 4,997,447; 5,002,581; 5,019,107; 5,041,140;5,049,393; 5,080,677; 5,108,446; 5,108,451; 5,116,374; 5,133,763;5,146,933; 5,147,406; 5,151,521; 5,156,631; 5,171,276; 5,181,925;5,197,987; 5,197,989; 5,201,881; 5,201,882; 5,217,498; 5,217,499;5,222,985; 5,282,868; 5,290,314; 5,314,478; 5,314,494; 5,316,550;5,326,376; 5,330,534; 5,314,493; 5,336,268; 5,344,459; 5,358,525;5,370,699; 5,376,064; 5,376,125; 5,387,244; 5,389,107; 5,405,403;5,405,411; 5,415,662; 5,425,779; 5,448,489; 5,458,643; 5,458,651;5,489,311; 5,491,882; 5,507,814; 5,507,818; 5,507,820; 5,507,823;5,507,830; 5,507,833; 5,507,836; 5,514,182; 5,514,184; 5,522,904;5,507,835; 5,246,461; 5,364,839; 5,376,120; 5,393,739; 5,480,449;5,510,418; 5,522,894; 4,892,551; 5,660,225; 4,089,071; 5,281,226;5,443,383; 5,480,437; 5,032,134; 4,997,444; 5,002,579; 5,443,512;5,133,762; 5,080,678; 5,944,759; 5,944,758; 5,944,757; 5,944,756;5,938,702; 5,935,174; 5,935,175; 5,935,173; 5,935,172; 5,935,171;5,931,871; 5,931,870; 5,928,289; 5,928,288; 5,928,287; 5,928,286;5,928,285; 5,919,236; 5,916,270; 5,916,269; 5,916,268; 5,913,858;5,911,759; 5,911,758; 5,910,172; 5,910,171; 5,906,644; 5,906,643;5,906,210; 5,904,720; 5,904,688; 5,902,340; 5,882,206; 5,888,204;5,879,407; 5,879,405; 5,879,404; 5,879,402; 5,879,401; 5,879,398;5,879,397; 5,879,396; 5,879,395; 5,879,393; 5,879,392; 5,879,390;5,879,387; 5,871,548; 5,871,547; 5,824,108; 5,824,107; 5,824,103;5,824,102; 5,824,101; 5,824,098; 5,800,560; 5,800,558; 5,800,557;5,800,555; 5,800,554; 5,800,553; 5,788,704; 5,782,928; 5,782,925;5,776,202; 5,766,260; 5,766,257; 5,755,811; 5,755,810; 5,755,804;5,755,801; 5,755,799; 5,743,918; 5,910,172; 5,211,666; 5,507,832;4,433,440; 5,397,359; 5,507,834; 5,314,492; 5,405,394; 5,316,550;5,314,494; 5,413,610; 5,507,835; 5,373,621; 5,433,750; 3,879,767;5,376,123; 5,480,437; 3,576,133; 5,376,126; 5,496,375; 3,600,718;5,108,449; 5,507,817; 5,181,929 and 5,507,829. Foreign patents DE2,247,721; EP 0,308,081; GB 2,126,096; GB 2,069,338; EP 0,190,446; EP0,066,092 and EP 0,253,941.

Foreign patents DE 2,247,721; EP 0,308,081; GB 2,126,096; GB 2,069,338;EP 0,190,446; EP 0,066,092 and EP 0,253,941.

SUMMARY OF THE INVENTION

The present invention seeks to provide improved joint and dentalimplants and methods relating to joint and tooth implantation byemploying a novel set of mechanical techniques which are interface withthe biological medium and improve anchoring to the surrounding bone.

It is known in the art that bones react to stress and strain accordingto Wolff's Law. Wolff's Law is known to express the biological responseto stress fields generated within the bone substance. The biologicalresponse to a certain normal stress magnitude generates the growth ofnew bone cells. The biological response to a certain extreme stressmagnitude does not generate the growth of new bone cells but causes boneresorption.

It is additionally known that bone adaptively responds to frequency andmagnitude of applied load. Therefore it can be stated that temporal andspatial regulation of loads may result in bone remodeling and overallincrease of bone mass. Furthermore, bone tissue of a wide range oforganisms remodels its shape and constitution to fit the same level ofstrain under normal activity. The application of different strain levelsresults in the growth of different types of cells: calcellous, corticalor cartilage.

It is further known in the art that in the vicinity of rigid implants,such as metal implants, there are regions of stress shielding in someparts of the bone, meaning that such rigid implants take load formerlytransferred to the bone, thereby shielding the bone from the load andcausing bone resorption. This process has been observed in regions suchas in the proximal medial bone after hip replacement, and such as underthe tibial component of knee replacements.

Prostheses described herein apply a set of design features which are allaimed at the utilization of the abovemensioned bone-growth properties.These include design of loading, interface configuration, mechanicalproperties of the pliable material from which the prostheses are formed,and the molding of deformation control elements within the prostheses.All of these, employed by persons skilled in the art, are expected toproduce desired controlled deformations within the prosthesis. Underthese combined conditions desired controlled deformations producedwithin the prosthesis substance are associated with the transmission ofcompression stress of desired magnitude distributed in desired regionwithin the prosthesis.

The present invention departs from prior art in the intentional handlingof stresses. While prior art allows for the presence of sharp or narrowfeatures in the resilient material design, the inventions describedherein adhere to the principles of fluid pressure management: inparticular, the pliable implant described in the invention maydistribute stresses in such a way that while load is exerted in one partof the implant, stress field develops in other regions, resembling theway stress is distributed by a contained fluid. Control of the crosssection may further determine pressures in a similar way to the flow offluid within a conduit. The preferred embodiments of the invention avoidsharp features in accordance with this principle, since sharp featuresimpede the flow of fluid and pressure lines.

The implants of the present invention comprise of flexible elements, andalso preferably include deformation control elements, resulting inimproved load distribution, which prevent or significantly reduce stressshielding.

One method of stress control is by interface geometry utilizingoversized thickness to exert constant compression stress. As discussedhereinabove, it is appreciated that the stresses produced in the naturalbone, such as in the natural acetabulum socket, produce correspondingstrains therein. Both the stresses and the strains have positive medicalimplications which are expressed in bone remodeling by growing new bonecells of structural characteristics. The resulting, long termregeneration of bone distributes stresses optimally within the bonesubstance. Distributing stresses optimally brings the stress conditionsas close as possible to the natural conditions. The improvedstress-field distribution at the interface between the prosthesis andthe bone helps prevent lysis.

Avoidance of bone resorption and deterioration and loss of bone geometryresponsible for sustaining the long term effectiveness of the mechanicallocking fixation of the artificial acetabulum socket is brought about bythe implant strain control in accordance with this invention describedhereinabove and more specific by the targeting of specific locationswithin the bone substance to be subjected to desired strain as isthought to promote bone regeneration and strengthening as detailed inbibliography known in the art cited hereinabove as opposed to the boneresorption and deterioration phenomena common in prior art devices.

There is thus provided in accordance with a preferred embodiment of thepresent invention an implantable artificial joint prosthesis includingat least one joint defining element defining a bone-engaging surface,the bone-engaging surface including an anchoring mechanism operative forenhancing anchoring and adhesion of the joint defining element to thebone and thus improving the stability and longevity of the prosthesis.

In accordance with another preferred embodiment of the present inventionan implantable tooth implant including at least one implant definingelement defining a bone-engaging surface, the bone-engaging surfaceincluding an anchoring mechanism operative for enhancing anchoring andadhesion of the implant defining element to the bone and thus improvingthe stability and longevity of the prosthesis.

In accordance with another preferred embodiment of the present inventionthe at least one joint defining element is formed of a material havingmechanical properties which are characterized by a nonlinear stressstrain relationship.

In accordance with yet another preferred embodiment of the presentinvention the at least one joint defining element defines a generallyhemispherical convex bone-engaging surface. Preferably, the at least onebone engagement surface has formed thereon a generally annular outwardlyextending protrusion.

Alternatively, the at least one joint defining element defines agenerally hemispherical concave bone-engaging surface. Preferably, theat least one bone engagement surface has formed thereon a generallyannular inwardly extending protrusion.

In accordance with another preferred embodiment of the present inventionthe protrusion defines a generally annular undercut.

In accordance with still another preferred embodiment of the presentinvention the at least one bone-engaging surface is arranged for snapfit engagement with a bone. Additionally or alternatively, the at leastone bone-engaging surface is arranged for press fit engagement with abone.

In accordance with a preferred embodiment of the present invention, theat least one bone-engaging surface is configured with a hexagonalconfiguration pattern. Preferably, the hexagonal configuration patternis defined by a plurality of protruding hexagonal contact surfaceportions, each surrounded by a peripheral channel. Alternatively, thehexagonal configuration pattern is defined by a plurality of recessedhexagonal contact surface portions, each surrounded by a peripheralchannel. Preferably, the channels are each defined by wall surfaces anda bottom surface. Additionally or alternatively, the channels aredefined to provide an undercut engagement portion.

In accordance with yet another preferred embodiment of the presentinvention the undercut engagement portion includes a relatively widercross sectional dimension near the bottom surface and a relativelynarrower cross sectional dimension away from the bottom surface.

In accordance with another preferred embodiment, the at least onebone-engaging surface is configured with a spiral configuration pattern.Preferably, the spiral configuration pattern is defined by spiralrecess. Additionally, the spiral recess is defined by wall surfaces anda bottom surface. Additionally or alternatively, the spiral recess isdefined to provide an undercut engagement portion. Preferably, theundercut engagement portion includes a relatively wider cross sectionaldimension near the bottom surface and a relatively narrower crosssectional dimension away from the bottom surface.

In accordance with still another preferred embodiment of the presentinvention the at least one bone-engaging surface is configured with apattern defined by a plurality of multidirectional generally radiallyextending elongate recesses. Preferably, the recesses are defined bywall surfaces and a bottom surface. Additionally or alternatively, therecesses are defined to provide an undercut engagement portion.Preferably, the undercut engagement portion includes a relatively widercross sectional dimension near the bottom surface and a relativelynarrower cross sectional dimension away from the bottom surface.

In accordance with another preferred embodiment of the present inventionthe at least one bone-engaging surface is configured with a geometricconfiguration pattern.

In accordance with yet another preferred embodiment of the presentinvention the at least one bone-engaging surface is configured with afractal configuration pattern.

Further in accordance with a preferred embodiment of the presentinvention the implantable artificial socket for a joint is adapted foruse as a tibial socket and defining an articulation portion having aconcave inner articulation surface and a bone engagement portion havinga bone engagement surface.

Preferably, the articulation portion is formed with a highly resilienthollow peripheral rim arranged for snap fit engagement with acorresponding peripheral socket formed in a surface of the boneengagement portion, opposite to the bone engagement surface.

Additionally in accordance with a preferred embodiment of the presentinvention the articulation portion is formed with a support protrusion,defining an undercut and arranged for resilient snap fit lockingengagement with a corresponding groove formed in the bone engagementportion.

Further in accordance with a preferred embodiment of the presentinvention the articulation surface has formed therein a plurality ofthroughgoing apertures and side openings, which allow synovial fluid topass therethrough for lubrication of the articulation surface.

Still further in accordance with a preferred embodiment of the presentinvention the implantable artificial socket for a joint is mounted ontoa tibia and arranged such that application of force to the joint causesthe articulation portion to be resiliently displaced toward the boneengagement portion, thus causing synovial fluid, located between thearticulation portion and the bone engagement portion, to be forcedthrough apertures and openings so as to lie on and over the articulationsurface and to provide enhanced lubrication for the articulation of anarticulation surface of a femur with the articulation surface.

Typically, the application of force causes the movement of thearticulation portion by resilient buckling of at least one protrusionand compression of a resilient rim and release of the force causesmovement of the articulation portion, accompanied by resilient return ofthe protrusion to its unstressed orientation and decompression of theresilient rim, wherein the application of force does not causesignificant deformation of the geometry of the articulation surface.

In accordance with a preferred embodiment of the present inventioninsertion of implants by gently positioning, gently engaging theartificial acetabulum socket at locations on an inner concave surfacethereof and pressing thereon in a direction generally along an axis ofsymmetry of the snap fit configured natural acetabulum, thereby causingdisplacement of the artificial acetabulum socket, which producesradially inward compression of the artificial acetabulum socket at theprotrusion and thereby resulting in deformation of the artificialacetabulum socket at the protrusion and in the general region thereof.

Further in accordance with a preferred embodiment of the presentinvention the radially inward compression and the resulting deformationof the artificial acetabulum socket produce stresses in the acetabulumsocket and cause forces to be applied to the acetabulum, producingcompression stresses and strains therein.

Additionally in accordance with a preferred embodiment of the presentinvention the displacement of the artificial acetabulum socket reducesthe separation between the planes of the outer edge of the implantableartificial acetabulum socket and the outer edge of the acetabulum.

Still further in accordance with a preferred embodiment of the presentinvention the method includes, following the gentle engaging, pressingfurther on the artificial acetabulum socket at locations on an innerconcave surface thereof, thereby causing further displacement of theartificial acetabulum socket producing sliding pressure engagementbetween an underlying surface portion of the protrusion at the undercutand a radially outward extending surface portion of the groove, whereinresiliency of the artificial acetabulum socket causes radially outwarddisplacement of the protrusion and corresponding radially outwarddecompression of the artificial acetabulum socket, resulting in reducedand changed stress patterns in both the artificial acetabulum socket andin the acetabulum.

Further in accordance with a preferred embodiment of the presentinvention the displacement of the artificial acetabulum socket furtherreduces the separation between the planes of the outer edge of theimplantable artificial acetabulum socket and the outer edge of theacetabulum.

Further in accordance with a preferred embodiment of the presentinvention the method further includes, following the pressing further,pressing on the artificial acetabulum socket at locations on edgesthereof, thereby causing further displacement of the artificialacetabulum socket and producing sliding snap fit engagement between theprotrusion and the groove, wherein the resiliency of the artificialacetabulum socket causes radially outward displacement of theprotrusion, thereby generally eliminating deformation of the artificialacetabulum socket at the protrusion and in the general region thereof.

Preferably, the snap fitting provides a generally non-press fitengagement, wherein touching engagement between the artificialacetabulum socket and the acetabulum produces stresses in both theacetabulum socket and in the acetabulum which are generally small andlocalized in the region of the snap fit engagement therebetween.

Further in accordance with a preferred embodiment of the presentinvention the snap fitting produces locking of the artificial acetabulumsocket in the groove and the undercut prevents disengagement of theprotrusion from the groove.

Additionally in accordance with a preferred embodiment of the presentinvention the snap fitting provides a generally press fit engagement,wherein touching engagement between the artificial acetabulum socket andthe acetabulum produces stresses in both the acetabulum socket and inthe acetabulum which are not localized in the region of the snap fitengagement therebetween.

Further in accordance with a preferred embodiment of the presentinvention the snap fitting in a generally press fit engagement producespressure engagement between the acetabulum and a convex facing surfaceof the artificial acetabulum socket generally along the entire extentthereof.

In accordance with a preferred embodiment of the present invention,additional stress fields exerted by external forces may be superimposedonto the stress fields produced by the snap fit and press fitengagements described hereinabove. Together with the external loadsproduced by loading of the joint, the stress field may be designed as tostimulate the growth of cells of structural characteristics.

In accordance with a preferred embodiment of the present invention,interface to the bone engaging surface may be configured over a limitedarea of the implant, or not configured at all, thus being particularlysuitable for patients with limited mobility and who are only capable oflow level of activity. It is appreciated that the fixation strengthachieved by press fit and snap fit alone is sufficient for the loadsimposed by the level of activity of such patients.

In accordance with a preferred embodiment of the present invention,implantable artificial acetabulum is not configured and is thereforeallowed to deform towards the rim of the acetabulum. In accordance withyet another preferred embodiment of the present invention, theapplication of texture and configuration to the outer rim of anacetabular socket implant results in improved fixation and may thusprevent the crawl of said socket under the reduced pressure present nearthe rim.

The present invention provides a dental implant which effectivelyadheres to the mandibular bone by transmitting forces which are similarin orientation and magnitude to those transmitted via the periodontalmembrane, thus preventing wear of the bone.

There is thus provided in accordance with a preferred embodiment of thepresent invention a bone engaging interface of an implantable toothimplant assembley, which is particularly suitable for use in a dentalfixture and may serve as an artificial periodontal ligament replacement.Said bone engaging interface is preferably formed by injection moldingof polyurethane, is preferably of generally uniform thickness, defininga concave inner fixture anchoring surface. Said bone engaging interfacemay have a beveled edge and a recess matched to provide for snap fitengagement of an implantable tooth implant assembly. Said bone engaginginterface having at least one generally annular outwardly extendingprotrusion arranged for snap fit engagement with a corresponding grooveformed by machining of a jaw bone. Preferably, said protrusion has across-section with an underlying slope sharper than the overlying slope.

There is further provided in accordance with a preferred embodiment ofthe present invention a method for implanting a peripheral andcontinuous recess between said protrusion and the rim of bone engaginginterface allowing for bone to grow into the recess and form aprotective barrier against germs.

It is also provided in accordance with a preferred embodiment of thepresent invention that the bone engaging interface is constructed from asingle layer, preferably, molded of a polyurethane, and includes aninserted internal deformation control element. Said deformation controlelement preferably constructed of a rigid material. Alternatively thedeformation control element is preferably formed of woven highperformance fibers. Said deformation control element is preferablycovered by PU inwardly, outwardly, and towards the rim. Said deformationcontrol element preferably has an overall generally annularconfiguration defined by a web portion and a thickened portion, and isfurther defined by rectangular cut-outs separated by flaps.

According to another preferred embodiment of the present invention thebone engaging interface incorporates a reinforcement constructed of highperformance fibers, which allows it to imitate the function of theperiodontal ligament.

In accordance with the principle described hereinabove the bone engaginginterface design avoids sharp and narrowed features, thus avoidingstress compression, and keeping said fibers strength.

In another preferred embodiment of the present invention, the boneengaging interface is configured from material layers and reinforcement,providing shock absorbing characteristics and allowing a small amount ofmovement of the tooth. Such movement is preferable in view of reasonsdescribed in detail hereinbelow. The shock absorbing capability thusprovided seeks to replace the functionality of the lost periodontalligament.

In accordance with another preferred embodiment of the present inventionthe relationship between the form and the dimensions of bone engaginginterface and the protrusion mounted upon it are, with respect to theform and the dimensions of the corresponding machined jaw bone,preferably arranged for press fit and snap fit engagement.

In accordance with a preferred embodiment of the present invention thebone engagement surface is configured with a pattern defined by aplurality of multidirectional generally radially extending elongatedrecesses. Said recesses are defined by wall surfaces and a bottomsurface where walls are preferably inclined outwardly toward the bottomsurface. It is a particular feature of these embodiments that when thebone engaging interface experiences forces and/or impacts, the resultingstresses and strains exerted within the jaw bone induce growth of newbone cells, which migrate into said recesses, creating an undercutlocking engagement with the interface.

In accordance with yet another preferred embodiment of the presentinvention, the generally annular outwardly extending protrusion mountedon the bone engaging interface is configured with a similarconfiguration pattern.

In accordance with another preferred embodiment of the presentinvention, the outer surface of the bone engaging interface ispreferably configured with a hexagonal configuration pattern.

Still further in accordance with a preferred embodiment of the presentinvention, preferably at least two ridge elements are integrally formedwith the rim of the bone engaging interface. These grip elementspreferably have an overall generally segmented or continuous annularconfiguration and are constructed operatively in accordance with stillanother preferred embodiment of the present invention to be gripped bythe jaws of an implanter tool.

In accordance with a preferred embodiment of the present invention adental crown prosthesis is mounted on a crown abutment preferablyconstructed from a shock absorbing material. The Crown abutment is fixedinto a fixture in the bone engaging interface.

In accordance with a preferred embodiment of the present invention thecrown abutment may be fixed to the bone engaging interface by fixinginto a fixture, or snap fitting, or alternatively snap fitting and pressfitting, or by a bayonet-type connection, or by screwing.

In accordance with a preferred embodiment of the present inventiondental fixture may be fixed to bone engaging interface by any ofsnap-fit, press-fit, bayonet-type connection or screwed.

In accordance with a preferred embodiment of the present invention thecrown abutment may be directly fixed into the bone engaging interfacewithout an intermediary element. All fixation method listed in theprevious paragraph may apply here as well.

Still further in accordance with a preferred embodiment of the presentinvention, the implantable tooth implant assembly is preferablyimplanted into the jaw bone by an implanter tool. The grip ridgeelements of the bone engaging interface are constructed and operative inaccordance with still another preferred embodiment of the presentinvention to be gripped by the jaws of an implanter tool. Said implantertool may be provided for the surgeon to perform the implanting of theimplantable dental implant simultaneously with the bone engaginginterface in one smooth installation process.

In accordance with a preferred embodiment of the present invention animplanter tool simultaneously stretch bone interface by grasping gripridge elements at the rim of the bone engaging interface and push theconcave inner fixture anchoring surface and by implanter tool element ordental implant.

In accordance with a preferred embodiment of the present invention, asurgeon using an implanter tool inserts into the suitably machined jawbone the implantable tooth assembly parts according to their order andthen proceeds to operate the implanter to continuously change flexingand pushing forces until the assembly parts are properly installed.

Still further in accordance with a preferred embodiment of the presentinvention, preferably grip ridge elements are formed on implantablesockets and operative with an implanter tool.

In accordance with a preferred embodiment of the present inventiontherein provided a flexible gum embankment element formed bone interfaceand extended outwardly and upwardly from the rim.

There is also provided in accordance with a preferred embodiment of thepresent invention an artificial femoral head prosthesis for use with anatural femoral head. This includes a bone interface element configuredto be mounted onto the natural femoral head, the bone interface elementhaving an inner concave surface which is configured to directly contactthe natural femoral head in generally static engagement therewith. Thebone interface element being particularly configured for retainable snapfit engagement with a suitably machine-shaped surface of the naturalfemoral head and a press fit acetabulum engagement element beingparticularly configured for retainable press fit engagement with thebone interface element. Having a smooth outer convex surface the implantis configured to be directly contacted by an acetabulum socket inmoveable engagement therewith.

In accordance with yet another preferred embodiment of the presentinvention all bone engaging implants described herein may include abioactive coating. Preferably, the bioactive coating is formed by gritblasting. Alternatively, the bioactive coating is formed by spraying. Inaccordance with another preferred embodiment, the bioactive coating alsoincludes an elastomer, or may be composite, including an elastomer andbioactive materials, such as Hydroxylapatite (HA). HA may resorb withtime. These bioactive materials cause the contact surface of theartificial implantation device to become bioactive, stimulating bonegrowth to provide an adhesion of the implant to the bone and accelerateosteointegration.

The feedstock for said coating can be in powder form or a PU rod or anycombination.

In accordance with a preferred embodiment of the present invention aspraying apparatus is used, where coating is preferably provided using acombustion process, directed by a nozzle. The process may start with apreheating step that is designed to melt the surface of the implant andprovide for a chemical bond between the surface and the polyurethaneparticles. Alternatively, a coating can be deposited onto the contactsurface of artificial the implantation device by means of dipping.

The coating may be an elastomer on elastomer coating.

In addition to the enhanced bone adhesion methods described herein, thecontact surface of an artificial implantation device may also be treatedusing one of the following Surface Modification processes: Atomiccleaning, adhesion promotion, molecular grafting, cell attachmentenhancement, and Plasma Enhanced Chemical Vapor Deposition (PECVD)coatings, such as implemented by the MetroLine Surface, Inc. Surfacemodification processes improve the articulating properties of thecontact surface by reducing friction and thereby enhance the resistanceto wear.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIGS. 1, 2, 3 and 4 are pictorial illustrations of an implantableartificial socket constructed and operative in accordance with apreferred embodiment of the present invention;

FIG. 5A is a simplified exploded view illustration of an implantableartificial tibial socket assembly constructed and operative inaccordance with a preferred embodiment of the present invention inassociation with a suitably machined tibia;

FIG. 5B is a simplified illustration a tibia, suitably machined toreceive the implantable artificial tibial socket assembly of FIG. 5A;

FIG. 6 is a simplified assembled view illustration of the implantableartificial tibial socket assembly of FIGS. 5A and 5B mounted onto atibia in accordance with a preferred embodiment of the presentinvention;

FIGS. 7A and 7B are sectional illustrations showing the implantableartificial tibial socket assembly of FIGS. 5A and 5B and FIG. 6 mountedonto a tibia in two alternative operative orientations;

FIGS. 8A and 8B are simplified exploded view illustrations of animplantable artificial femoral surface element assembly constructed andoperative in accordance with a preferred embodiment of the presentinvention;

FIG. 9 is a simplified assembled view illustration of the implantableartificial femoral surface element assembly of FIG. 8A mounted onto atibia in accordance with a preferred embodiment of the presentinvention;

FIGS. 10A and 10B are sectional illustrations showing the implantableartificial tibial socket assembly of FIGS. 8A and 8B and FIG. 9 mountedonto a tibia in two alternative operative orientations;

FIGS. 11A and 11B are sectional illustrations showing the implantableartificial tibial socket assembly of FIG. 5A to FIG. 7B and theimplantable artificial femoral surface element assembly of FIG. 8A toFIG. 10B in respective first and second operative orientations in atotal unicondylar knee replacement environment;

FIG. 60 is a simplified meshed sectional illustration of a first stagein a press fit and snap fit installation of an implantable artificialsocket in a reamed acetabulum in accordance with a preferred embodimentof the present invention;

FIG. 61 is a simplified meshed sectional illustration of a second stagein a press fit and snap fit installation of an implantable artificialsocket in a reamed acetabulum in accordance with a preferred embodimentof the present invention, showing stress fields;

FIG. 62 is a simplified meshed sectional illustration of a third stagein a press fit and snapfit installation of an implantable artificialsocket in a reamed acetabulum in accordance with a preferred embodimentof the present invention, showing stress fields;

FIG. 63 is a simplified meshed sectional illustration of a final stagein a press fit and snap fit installation of an implantable artificialsocket in a reamed acetabulum in accordance with a preferred embodimentof the present invention, showing stress fields;

FIGS. 64A and 64B are respective pictorial and partially cut awayillustrations of a bone engaging interface of an implantable tooth rootimplant constructed and operative in accordance with a preferredembodiment of the present invention;

FIGS. 65A and 65B are sectional illustrations of an implantable toothimplant assembly mounted onto a jaw bone in accordance with a preferredembodiments of the present invention;

FIG. 66 is a pictorial and partially cut away illustration of a boneengaging interface of an implantable tooth root implant mounted onto ajaw bone in accordance with a preferred embodiments of the presentinvention constructed and operative in accordance with a preferredembodiment of the present invention;

FIGS. 74A and 74B are simplified meshed sectional illustrations of anartificial hip joint constructed and operative in accordance with apreferred embodiment of the present invention, showing stress fieldsproduced by press fit installation of an implantable artificial socket;

FIGS. 75A and 75B are simplified meshed sectional illustrations of theartificial hip joint of FIG. 74, showing changed stress fields resultingfrom loading of the joint;

FIGS. 76A and 76B are simplified meshed sectional illustrations of anartificial hip joint constructed and operative in accordance withanother preferred embodiment of the present invention, showing stressfields resulting from loading of the joint which are modified byprovision of deformation control layers in the implantable artificialsocket and by variations in the thickness of an implantable artificialsocket;

FIGS. 77A and 77B are simplified meshed sectional illustrations of anartificial hip joint constructed and operative in accordance withanother preferred embodiment of the present invention, showing stressfields resulting from loading of the joint which are modified byprovision of deformation control elements in the implantable artificialsocket;

FIGS. 78A and 78B is a simplified meshed sectional illustration of anartificial hip joint constructed and operative in accordance withanother preferred embodiment of the present invention, showing stressfields resulting from loading of the joint which are modified byprovision of deformation control elements in an implantable artificialfemoral head surface element formed on a femoral head articulatingtherewith;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1, which is a pictorial illustration of animplantable artificial socket constructed and operative in accordancewith a preferred embodiment of the present invention and which isparticularly suitable for use in a hip joint. The embodiment of FIG. 1is particularly directed to providing an anchoring mechanism on abone-engaging surface of the artificial socket for enhancing theanchoring and adhesion of the socket to the bone and thus improving thestability and longevity of the prosthesis.

As seen in FIG. 1, an implantable artificial socket, designated byreference numeral 1100, is formed preferably by injection molding of abio stable and bio compatible pliable material such as an elastomer,preferably polyurethane, having mechanical properties which arecharacterized by a nonlinear stress strain relationship.

Preferably, implantable artificial socket 1100 is of generally uniformthickness and defines a generally hemispherical convex bone engagementsurface 1101 and a partially hemispherical convex bone engagementsurface 1104 which preferably have formed thereon, at any suitablelocation between its apex 1102 and its rim 1103, a generally annularoutwardly extending protrusion 1106, preferably defining a generallyannular undercut 1108. Alternatively, the protrusion 1106 may be anyother suitable annular or non-annular, continuous or discontinuous,generally peripheral, protrusion. The protrusion 1106 is preferablyarranged for snap fit engagement with a corresponding groove formed byreaming of a bone.

In accordance with another preferred embodiment of the presentinvention, the relationship between the form and the dimensions ofimplantable artificial socket 1100 and the protrusion 1106 are, withrespect to the form and the dimensions of the corresponding reamed bone,preferably arranged for press fit and snap fit engagement with the bone.The press fit feature is typically provided by making the outerdimensions of socket 1100 slightly larger than the correspondingdimensions of the machined bone surface onto which the socket fits.

The convex bone engagement surface 1101 is preferably configured with ahexagonal configuration pattern 1110, preferably defined by a pluralityof protruding hexagonal contact surface portions 1112, each surroundedby a peripheral channel 1114. Channels 1114 are defined by wall surfaces1116 and a bottom surface 1120. In accordance with a preferredembodiment of the present invention, channels 1114 are configured withwall surfaces 1116 being inclined outwardly toward the bottom surface1120, creating an undercut configuration having a relatively wider crosssectional dimension near the bottom surface and a relatively narrowercross sectional dimension away from the bottom surface.

It is a particular feature of the embodiment of FIG. 1 that when theartificial joint equipped with implantable artificial socket 1100experiences forces and/or impacts, such as those having a cyclic natureresulting from walking or running, the resulting stresses and strainsexerted within the bone in proximity to the bone engagement surface 1101induce growth of new bone cells, which, gradually, over time migrateinto the channels 1114. The new bone cells typically press on othercells, creating remodeling of the bone in engagement with boneengagement surface 1101, causing the bone to migrate into the channels1114 gradually, over time, and thus create an undercut lockingengagement with the socket 1100.

In accordance with another preferred embodiment of the presentinvention, the partially hemispherical convex bone engagement surface1104 is preferably configured with a configuration pattern similar tothe hexagonal configuration pattern 1110.

In accordance with yet another preferred embodiment of the presentinvention, the generally annular outwardly extending protrusion 1106 ispreferably configured with a configuration pattern similar to thehexagonal configuration pattern 1110 or configured with a pattern madeof pattern segments similar to the hexagonal configuration pattern 1110.

Reference is now made to FIG. 2, which is a pictorial illustration of animplantable artificial socket constructed and operative in accordancewith a preferred embodiment of the present invention and which isparticularly suitable for use in a hip joint. The embodiment of FIG. 2is also particularly directed to providing an anchoring mechanism on abone-engaging surface of the artificial socket for enhancing theanchoring and adhesion of the socket to the bone and thus improving thestability and longevity of the prosthesis.

As seen in FIG. 2, an implantable artificial socket, designated byreference numeral 1200, is formed preferably by injection molding of abio stable and bio compatible pliable material such as an elastomer,preferably polyurethane, having mechanical properties which arecharacterized by a nonlinear stress strain relationship.

Preferably, implantable artificial socket 1200 is of generally uniformthickness and defines a generally hemispherical convex bone engagementsurface 1201 and a partially hemispherical convex bone engagementsurface 1204 which preferably have formed thereon, at any suitablelocation between its apex 1202 and its rim 1203, a generally annularoutwardly extending protrusion 1206 similar to a generally annularoutwardly extending protrusion 1106 as shown in FIG. 1 hereinabove,preferably defining a generally annular undercut 1208. Alternatively,the protrusion 1206 may be any other suitable annular or non-annular,continuous or discontinuous, generally peripheral, protrusion. Theprotrusion 1206 is preferably arranged for snap fit engagement with acorresponding groove formed by reaming of a bone.

In accordance with another preferred embodiment of the presentinvention, the relationship between the form and the dimensions ofimplantable artificial socket 1200 and the protrusion 1206 are, withrespect to the form and the dimensions of the corresponding reamed bone,preferably arranged for press fit and snap fit engagement with the bone.The press fit feature is typically provided by making the outerdimensions of socket 1200 slightly larger than the correspondingdimensions of the machined bone surface onto which the socket fits.

The convex bone engagement surface 1201 is preferably configured with ahexagonal configuration pattern 1210 preferably defined by a pluralityof recessed hexagonal contact surface portions 1212, each surrounded bya peripheral ridge 1214. Ridges 1214 are defined by wall surfaces 1216and a top surface 1220. In accordance with a preferred embodiment of thepresent invention, ridges 1214 are configured with wall surfaces 1216being inclined outwardly toward the top surface 1220, creating anundercut configuration at said recessed hexagonal contact surfaceportions 1212 having a relatively wider cross sectional dimension nearsurface portions 1212 and a relatively narrower cross sectionaldimension away from the surface portions 1212.

It is a particular feature of the embodiment of FIG. 2 that when theartificial joint equipped with implantable artificial socket 1200experiences forces and/or impacts, such as those having a cyclic natureresulting from walking or running, the resulting stresses and strainsexerted within the bone in proximity to the bone engagement surface 1201induce growth of new bone cells, which, gradually, over time, migrateinto the regions above surface portions 1212. The new bone cellstypically press on other cells, creating remodeling of the bone inengagement with bone engagement surface 1201, causing the bone tomigrate into the regions above surface portions 1212 gradually, overtime, and thus create an undercut locking engagement with the socket1200.

In accordance with another preferred embodiment of the presentinvention, the partially hemispherical convex bone engagement surface1204 is preferably configured with a configuration pattern similar tothe hexagonal configuration pattern 1210.

In accordance with yet another preferred embodiment of the presentinvention, the generally annular outwardly extending protrusion 1206 ispreferably configured with a configuration pattern similar to thehexagonal configuration pattern 1210 or configured with a pattern madeof pattern segments similar to the hexagonal configuration pattern 1210.

Reference is now made to FIG. 3, which is a pictorial illustration of animplantable artificial socket constructed and operative in accordancewith a preferred embodiment of the present invention and which isparticularly suitable for use in a hip joint.

As seen in FIG. 3, an implantable artificial socket, designated byreference numeral 2100, is formed preferably by injection molding of abio stable and bio compatible pliable material such as an elastomer,preferably polyurethane, having mechanical properties which arecharacterized by a nonlinear stress strain relationship.

Preferably, implantable artificial socket 2100 is of generally uniformthickness and defines a generally hemispherical convex bone engagementsurface 2101 and a partially hemispherical convex bone engagementsurface 2104 which preferably have formed thereon, at any suitablelocation between its apex 2102 and its rim 2103, a generally annularoutwardly extending protrusion 2106 similar to a generally annularoutwardly extending protrusion 1106 as shown in FIG. 1 hereinabove,preferably defining a generally annular undercut 2108. Alternatively,the protrusion 2106 may be any other suitable annular or non-annular,continuous or discontinuous, generally peripheral, protrusion. Theprotrusion 2106 is preferably arranged for snap fit engagement with acorresponding groove formed by reaming of a bone.

In accordance with another preferred embodiment of the presentinvention, the relationship between the form and the dimensions ofimplantable artificial socket 2100 and the protrusion 2106 are, withrespect to the form and the dimensions of the corresponding reamed bone,preferably arranged for press fit and snap fit engagement with the bone.The press fit feature is typically provided by making the outerdimensions of socket 2100 slightly larger than the correspondingdimensions of the machined bone surface onto which the socket fits.

The convex bone engagement surface 2101 is preferably configured with aspiral configuration pattern 2110 preferably defined by a recess 2112configured in a spiral. Spiral recess 2112 is defined by wall surfaces2116 and a bottom surface 2120. In accordance with a preferredembodiment of the present invention, spiral recess 2112 is configuredwith wall surfaces 2116 being inclined outwardly toward the bottomsurface 2120, creating an undercut configuration having a relativelywider cross sectional dimension near the bottom surface and a relativelynarrower cross sectional dimension away from the bottom surface. It isappreciated that, even though the illustrated embodiment shows acircular spiral configuration pattern 2110, any suitable spiralconfiguration pattern, such as an elliptic or non-symmetric spiralpattern, or any combination thereof, may be provided.

It is a particular feature of the embodiment of FIG. 3 that when theartificial joint equipped with implantable artificial socket 2100experiences forces and/or impacts, such as those having a cyclic natureresulting from walking or running, the resulting stresses and strainsexerted within the bone in proximity to the bone engagement surface 2101induce growth of new bone cells, which, gradually, over time, migrateinto the spiral recess 2112. The new bone cells typically press on othercells, creating remodeling of the bone in engagement with boneengagement surface 2101, causing the bone to migrate into the spiralrecess 2102 gradually over time and thus create an undercut lockingengagement with the socket 2100. In accordance with another preferredembodiment of the present invention, the partially hemispherical convexbone engagement surface 2104 is preferably configured with aconfiguration pattern similar to the hexagonal configuration pattern2110.

In accordance with yet another preferred embodiment of the presentinvention, the generally annular outwardly extending protrusion 2106 ispreferably configured with a configuration pattern similar to thehexagonal configuration pattern 2110 or configured with a pattern madeof pattern segments similar to the hexagonal configuration pattern 2110.

Reference is now made to FIG. 4, which is a pictorial illustration of animplantable artificial socket constructed and operative in accordancewith a preferred embodiment of the present invention and which isparticularly suitable for use in a hip joint.

As seen in FIG. 4, an implantable artificial socket, designated byreference numeral 2200, is formed preferably by injection molding of abio stable and bio compatible pliable material such as an elastomer,preferably polyurethane, having mechanical properties which arecharacterized by a nonlinear stress strain relationship.

Preferably, implantable artificial socket 2200 is of generally uniformthickness and defines a generally hemispherical convex bone engagementsurface 2201 and a partially hemispherical convex bone engagementsurface 2204 which preferably have formed thereon, at any suitablelocation between its apex 2202 and its rim 2203, a generally annularoutwardly extending protrusion 2206 similar to a generally annularoutwardly extending protrusion 1106 as shown in FIG. 1 hereinabove,preferably defining a generally annular undercut 2208. Alternatively,the protrusion 2206 may be any other suitable annular or non-annular,continuous or discontinuous, generally peripheral, protrusion. Theprotrusion 2206 is preferably arranged for snap fit engagement with acorresponding groove formed by reaming of a bone.

In accordance with another preferred embodiment of the present inventionthe relationship between the form and the dimensions of implantableartificial socket 2200 and the protrusion 2206 are, with respect to theform and the dimensions of the corresponding reamed bone, preferablyarranged for press fit and snap fit engagement with the bone. The pressfit feature is typically provided by making the outer dimensions ofsocket 2200 slightly larger than the corresponding dimensions of themachined bone surface onto which the socket fits.

The convex bone engagement surface 2201 is preferably configured with apattern 2210 preferably defined by a plurality of multidirectionalgenerally radially extending elongate recesses 2214. Recesses 2214 aredefined by wall surfaces 2216 and a bottom surface 2220. In accordancewith a preferred embodiment of the present invention, recesses 2214 areconfigured with wall surfaces 2216 being inclined outwardly toward thebottom surface 2220, creating an undercut configuration having arelatively wider cross sectional dimension near the bottom surface and arelatively narrower cross sectional dimension away from the bottomsurface.

It is a particular feature of the embodiment of FIG. 4 that when theartificial joint equipped with implantable artificial socket 2200experiences forces and/or impacts, such as those having a cyclic natureresulting from walking or running, the resulting stresses and strainsexerted within the bone in proximity to the bone engagement surface 2201induce growth of new bone cells, which, gradually, over time, migrateinto the recesses 2214. The new bone cells typically press on othercells, creating remodeling of the bone in engagement with boneengagement surface 2201, causing the bone to migrate into the channels2214 gradually, over time, and thus create an undercut lockingengagement with the socket 2200.

It is appreciated that the hexagonal configuration pattern 1110 of FIG.1 and the hexagonal configuration pattern 1210 of FIG. 2 areapproximately obverse versions of the same pattern. It is appreciatedthat similar obverse versions of the configuration patterns of FIGS. 3and 4 may also be provided. It is further appreciated that theillustrated patterns are intended as examples only, and any suitableconfiguration pattern, such as geometric or fractal patterns, may alsobe provided.

It is further appreciated that even though the illustrated embodimentscomprise continuous configuration patterns, prostheses comprising anysuitable combination of continuous or discontinuous configurationpatterns, covering all or selected portions of the bone contact surface,may also be provided. In accordance with another preferred embodiment ofthe present invention, the partially hemispherical convex boneengagement surface 2204 is preferably configured with a configurationpattern similar to the hexagonal configuration pattern 2210.

In accordance with yet another preferred embodiment of the presentinvention, the generally annular outwardly extending protrusion 2206 ispreferably configured with a configuration pattern similar to thehexagonal configuration pattern 2210 or configured with a pattern madeof pattern segments similar to the hexagonal configuration pattern 2210.

It is further appreciated that in preferred embodiments of implantsdescribed in FIGS. 1-4 hereinabove implants may be constructed with anyof the following: Where the material of the bone interface element beingmore flexible than that of bone; Where bone interface element is formedwith at least one hollow portion; Where bone interface element containsat least one passageway for fluids; Where bone interface element isshock-absorbing; and wherein bone interface has mechanical properties ofmammalian cartilage; Where bone interface is more resilient that theacetabulum or femoral head;

Where bone-interfacing element, connected to a first bone of a joint,articulates with a second element. Where said articulation may bemechanically delimited. Where an acetabular implant articulates with anartificial ball; Where ball has at least one delimiting element; Whereball delimiting element is constructed as a protrusion; where ball ismore shock absorbing then the femur and acetabulum; Where ball is formedwith a plurality of portions having different mechanical properties;where the plurality of portions are omega shaped; Where ball comprisesan outer shell and an inner core; wherein said artificial ball is formedwith a plurality of alternating adjacent first and second portions, saidfirst portions being generally more rigid than said second portions.Where artificial ball is formed with hollows filled with fluids; Whereartificial ball is formed with hollows and passageways for fluids; wheresaid fluids are the synovial fluids;

Where said first and said second joint portions articulate with a thirdintermediate portion. Where motion with respect to said third portion ismechanically delimited;

Where bone-interface comprises at least two layers;

Where bone engaging element and artificial articulating element areseparate. Where said bone engaging element and articulating element areconnected by snap-fit, bayonet or thread.

Where bone interface element has a cut-out portion; where there isprovided a fitting element for engagement at said cut out portion; wherethere is provided a locking portion for said engagement; where boneinterface element is configured to receive the prongs of an insertiontool;

It is further appreciated that the abovementioned preferred embodimentsmay be deployed by a minimally invasive surgical technique, wherein ajoint prosthesis comprising an artificial socket formed by expansion ofan artificial socket precursor of relatively reduced dimensions, isconfigured for insertion into a joint environment with reduceddisturbance of joint ligaments, said expansion taking place in situbetween existing ligaments to a desired socket shape.

Reference is now made to FIG. 5A, which is a simplified exploded viewillustration of an implantable artificial tibial socket assemblyconstructed and operative in accordance with a preferred embodiment ofthe present invention in association with a suitably machined tibia andto FIG. 5B, which is a simplified illustration a tibia, suitablymachined to receive the implantable artificial tibial socket assembly ofFIG. 5A and to FIG. 6 which is a simplified illustration of implantableartificial tibial socket assembly assembled unto tibia 3934 andconstructed and operative in accordance with a preferred embodiment ofthe present invention.

As seen in FIGS. 5A and 5B, an implantable artificial tibial socketassembly, designated by reference numeral 3900, is formed preferably byinjection molding of a bio stable and bio compatible pliable materialsuch as an elastomer, preferably polyurethane, having mechanicalproperties which are characterized by a nonlinear stress strainrelationship.

Preferably, implantable artificial socket assembly 3900 defines aconcave articulation surface 3902, which is defined on an articulationportion 3903, and a bone engagement surface 3904, which is defined on abone engagement portion 3905. Bone engagement surface 3904 preferablyhas formed thereon multiple protrusions. In the illustrated embodiment,there are provided an inner protrusion 3906 and an outer peripheralprotrusion 3908, defining respective undercuts 3910 and 3912.Alternatively, protrusions 3906 and 3908 may be any other suitable openor closed protrusions. Protrusions 3906 and 3908 are preferably arrangedfor snap fit engagement with corresponding grooves 3914 and 3916provided by machining of the tibia.

In accordance with a preferred embodiment of the present invention, boneengagement surface 3904 has formed thereon a pattern 3917 defined by aplurality of multidirectional elongate recesses 3918 similar to thepattern 2210 shown in FIG. 4. Alternatively, pattern 3917 may be ahexagonal configuration pattern, similar to pattern 1110 of FIG. 1 or1210 of FIG. 2, or a spiral configuration pattern similar to pattern2110 of FIG. 3. Additionally, as described hereinabove, obverse patternsof these patterns or any other suitable configuration pattern may alsobe provided.

Recesses 3918 are configured with wall surfaces 3919 and a bottomsurface 3920. In accordance with a preferred embodiment of the presentinvention recesses 3918 are configured to have wall surfaces 3919inclined outwardly toward bottom surface 3920, creating an undercutconfiguration having a relatively wider cross sectional dimension nearthe bottom surface and a relatively narrower cross sectional dimensionaway from the bottom surface.

Articulation portion 3903 is formed with a highly resilient hollowperipheral rim 3921 arranged for snap fit engagement with acorresponding peripheral socket 3922 formed in a surface of boneengagement portion 3905, opposite to bone engagement surface 3904thereof. Articulation portion 3903 also is formed with a supportprotrusion 3923, defining an undercut 3924 and arranged for resilientsnap fit locking engagement with a corresponding groove 3926 formed inbone engagement portion 3905.

In accordance with a preferred embodiment of the present invention,articulation portion 3903 has formed in articulation surface 3902 aplurality of thoroughgoing apertures 3928 and side openings 3930, whichallow synovial fluid to pass therethrough for lubrication of thearticulation surface 3902.

It is a particular feature of the embodiment of FIG. 5A that when theartificial joint equipped with implantable artificial tibial socketassembly 3900 experiences forces and/or impacts, such as those having acyclic nature resulting from walking or running, the resulting stressesand strains exerted within the bone in proximity to the bone engagementsurface 3904 induce growth of new bone cells, which, gradually, overtime, migrate into the recesses 3918. The new bone cells typically presson other cells, creating remodeling of the bone in engagement with boneengagement surface 3904, causing the bone to migrate into the recesses3918 gradually, over time, and thus create an undercut lockingengagement with the socket assembly 3900.

It is noted as seen in FIG. 6 and also in FIGS. 7A and 7B below thatimplantable artificial tibial socket assembly 3900 assembled unto tibia3934 is shown as an embodiment of the present invention wherein nopattern such as the pattern 3917 is formed on bone engagement surface3904. The bone engagement surface 3904 may be formed additionally, asdescribed hereinabove, obverse patterns of these patterns or any othersuitable configuration pattern or any other non-smooth textures may alsobe provided.

Reference is now made to FIGS. 7A and 7B, which are sectionalillustrations showing the implantable artificial tibial socket assemblyof FIGS. 29 & 30 mounted onto a tibia in two alternative operativeorientations. FIG. 31A shows an operative orientation wherein the jointis loaded, e.g. the femur, here designated by reference numeral 3932,presses downward onto the tibia, here designated by reference numeral3934. The loading force is designated by arrow 3936.

As seen in FIG. 7A, application of force 3936 causes the articulationportion 3903 to be resiliently displaced toward the bone engagementportion 3905, thus causing synovial fluid, located between thearticulation portion 3903 and the bone engagement portion 3905 to beforced through apertures 3928 and openings 3930 so as to lie on and overarticulation surface 3902 and to provide enhanced lubrication for thearticulation of an articulation surface 3938 of femur 3932 witharticulation surface 3902.

Considering FIGS. 7A and 7B, it is seen that the application of force3936, causes movement of articulation portion 3903 as indicated byarrows 3940, and corresponding flow of synovial fluid as indicated byarrows 3942. This movement is accompanied by resilient buckling ofprotrusion 3922, as indicated by arrows 3944 and compression ofresilient rim 3918, as indicated by arrows 3946.

Release of force 3936 causes movement of articulation portion 3903 asindicated by arrows 3950, and corresponding flow of synovial fluid asindicated by arrows 3952. This movement is accompanied by resilientreturn of protrusion 3922 to its unstressed orientation, as indicated byarrows 3954 and decompression of resilient rim 3918, as indicated byarrows 3956.

It is a particular feature of the construction of articulation portion3903 and of bone engagement portion 3905 that the application of force3936 does not cause significant deformation of the geometry ofarticulation surface 3902.

It is an additional particular feature of the construction ofarticulation portion 3903 and of bone engagement portion 3905 that wearor deformation of the articulation surface 3902 may be relatively easilyremedied by “plug-in” snap fit replacement of the articulation portion3903 into engagement with the bone engagement portion 3905, which neednot necessarily be replaced.

Reference is now made to FIGS. 8A and 8B, which is a simplified explodedview illustration of an implantable artificial femoral surface elementassembly constructed and operative in accordance with a preferredembodiment of the present invention in association with a suitablymachined femur and to FIG. 8B, which is a simplified illustration of afemur, suitably machined to receive the implantable artificial femoralsurface element assembly of FIG. 8A and to FIG. 9 which is a simplifiedillustration of implantable artificial femoral surface element assemblyassembled unto femur 4032 and constructed and operative in accordancewith a preferred embodiment of the present invention.

As seen in FIGS. 8A and 8B, an implantable artificial femoral surfaceelement assembly, designated by reference numeral 4000, is formedpreferably by injection molding of a bio stable and bio compatiblepliable material such as an elastomer, preferably polyurethane, havingmechanical properties which are characterized by a nonlinear stressstrain relationship.

Preferably, implantable artificial socket assembly 4000 defines a convexarticulation surface 4002, which is defined on an articulation portion4003, and a bone engagement surface 4004, which is defined on a boneengagement portion 4005. Bone engagement surface 4004 preferably hasformed thereon multiple protrusions.

In the illustrated embodiment, there are provided an inner protrusion4006 and an outer peripheral protrusion 4008, defining respectiveundercuts 4010 and 4012. Alternatively, protrusions 4006 and 4008 may beany other suitable open or closed protrusions. Protrusions 4006 and 4008are preferably arranged for snap fit engagement with correspondinggrooves 4014 and 4016 provided by machining of a femur medial condyle.

In accordance with a preferred embodiment of the present invention, boneengagement surface 4004 has formed thereon a pattern 4017 defined by aplurality of multidirectional elongate recesses 4018 similar to thepattern 2210 shown in FIG. 4. Alternatively, pattern 4017 may be ahexagonal configuration pattern, similar to pattern 1110 of FIG. 1 or1210 of FIG. 2, or a spiral configuration pattern similar to pattern2110 of FIG. 3. Additionally, as described hereinabove, obverse patternsof these patterns or any other suitable configuration pattern may alsobe provided.

Recesses 4018 are configured with wall surfaces 4019 and a bottomsurface 4020. In accordance with a preferred embodiment of the presentinvention recesses 4018 are configured to have wall surfaces 4019inclined outwardly toward bottom surface 4020, creating an undercutconfiguration having a relatively wider cross sectional dimension nearthe bottom surface and a relatively narrower cross sectional dimensionaway from the bottom surface.

Articulation portion 4003 is formed with a highly resilient hollowperipheral rim 4021 arranged for snap fit engagement with acorresponding peripheral socket 4022 formed in a surface of boneengagement portion 4005, opposite to bone engagement surface 4004thereof. Articulation portion 4003 also is formed with a supportprotrusion 4023, defining an undercut 4024, and arranged for resilientsnap fit locking engagement with a corresponding groove 4026 formed inbone engagement portion 4005.

In accordance with a preferred embodiment of the present invention,articulation portion 4003 has formed in articulation surface 4002 aplurality of thoroughgoing apertures 4028 and side openings 4030, whichallow synovial fluid to pass therethrough for lubrication of thearticulation surface 4002.

It is a particular feature of the embodiment of FIGS. 8A and 8B thatwhen the artificial joint equipped with implantable artificial femoralsurface element assembly 4000 experiences forces and/or impacts, such asthose having a cyclic nature resulting from walking or running, theresulting stresses and strains exerted within the bone in proximity tothe bone engagement surface 4004 induce growth of new bone cells whichgradually over time migrate into the recesses 4018. The new bone cellstypically press on other cells, creating remodeling of the bone inengagement with bone engagement surface 4004, causing the bone tomigrate into the recesses 4018 gradually over time and thus to create anundercut locking engagement with the socket assembly 4000.

It is noted as seen in FIG. 9 and also in FIGS. 10A and 10B below thatimplantable artificial femoral surface element assembly 4000 assembledunto femur 4032 is shown as an embodiment of the present inventionwherein no pattern such as the pattern 4017 is formed on bone engagementsurface 4004. The bone engagement surface 4004 may be formedadditionally, as described hereinabove, obverse patterns of thesepatterns or any other suitable configuration pattern or any othernon-smooth textures may also be provided.

Reference is now made to FIGS. 10A and 10B, which are sectionalillustrations showing the implantable artificial femoral surface elementassembly of FIG. 8A mounted onto a femoral medial condyle 4032 in twoalternative operative orientations. FIG. 10A shows an operativeorientation wherein the joint is loaded, e.g. the femur, here designatedby reference numeral 4032, presses downward onto the tibia, heredesignated by reference numeral 4034. The loading force is designated byarrow 4036.

As seen in FIG. 10A, application of force 4036 causes the articulationportion 4003 to be resiliently displaced toward the bone engagementportion 4005, thus causing synovial fluid, located between thearticulation portion 4003 and the bone engagement portion 4005 to beforced through apertures 4028 and openings 4030 so as to lie on and overarticulation surface 4002 and to provide enhanced lubrication for thearticulation of an articulation surface 4038 of tibia 4034 witharticulation surface 4002.

Considering FIGS. 10A and 10B, it is seen that the application of force4036, causes movement of articulation portion 4003 as indicated byarrows 4040, and corresponding flow of synovial fluid as indicated byarrows 4042. This movement is accompanied by resilient buckling ofprotrusion 4022, as indicated by arrows 4044 and compression ofresilient rim 4018, as indicated by arrows 4046.

Release of force 4036 causes movement of articulation portion 4003 asindicated by arrows 4050, and corresponding flow of synovial fluid asindicated by arrows 4052. This movement is accompanied by resilientreturn of protrusion 4022 to its unstressed orientation, as indicated byarrows 4054 and decompression of resilient rim 4018, as indicated byarrows 4056.

It is a particular feature of the construction of articulation portion4003 and of bone engagement portion 4005 that the application of force4036 does not cause significant deformation of the geometry ofarticulation surface 4002.

It is an additional particular feature of the construction ofarticulation portion 4003 and of bone engagement portion 4005 that wearor deformation of the articulation surface 4002 may be relatively easilyremedied by “plug-in” snap fit replacement of the articulation portion4003 into engagement with the bone engagement portion 4005, which neednot necessarily be replaced.

Reference is now made to FIGS. 11A and 11B, which are sectionalillustrations showing the implantable artificial tibial socket assemblyof FIGS. 5A-7B and the implantable artificial femoral surface elementassembly of FIGS. 8A-10B in respective first and second operativeorientations in a total unicondylar knee replacement environment.

As seen in FIG. 11A, application of force 3936 causes the articulationportion 3903 to be resiliently displaced toward the bone engagementportion 3905, thus causing synovial fluid, located between thearticulation portion 3903 and the bone engagement portion 3905 to beforced through apertures 3928 and openings 3930 so as to lie on and overarticulation surface 3902 and to provide enhanced lubrication for thearticulation of an articulation surface 3938 of femur 3932 witharticulation surface 3902.

It is seen that the application of force 3936, causes movement ofarticulation portion 3903 as indicated by arrows 3940, and correspondingflow of synovial fluid as indicated by arrows 3942. This movement isaccompanied by resilient buckling of protrusion 3922, as indicated byarrows 3944 and compression of resilient rim 3918, as indicated byarrows 3946.

As also seen in FIG. 11A, application of force 3936 causes thearticulation portion 4003 to be resiliently displaced toward the boneengagement portion 4005, thus causing synovial fluid, located betweenthe articulation portion 4003 and the bone engagement portion 4005 to beforced through apertures 4028 and openings 4030 so as to lie on and overarticulation surface 4002 and to provide enhanced lubrication for thearticulation of an articulation surface 4038 of tibia 4034 witharticulation surface 4002.

It is noted that the application of force 3936, causes movement ofarticulation portion 4003 as indicated by arrows 4040, and correspondingflow of synovial fluid as indicated by arrows 4042. This movement isaccompanied by resilient buckling of protrusion 4022, as indicated byarrows 4044 and compression of resilient rim 4018, as indicated byarrows 4046.

Release of force 3936 causes movement of articulation portion 3903 asindicated by arrows 3950, and corresponding flow of synovial fluid asindicated by arrows 3952. This movement is accompanied by resilientreturn of protrusion 3922 to its unstressed orientation, as indicated byarrows 3954 and decompression of resilient rim 3918, as indicated byarrows 3956.

Release of force 3936 also causes movement of articulation portion 4003as indicated by arrows 4050, and corresponding flow of synovial fluid asindicated by arrows 4052. This movement is accompanied by resilientreturn of protrusion 4022 to its unstressed orientation, as indicated byarrows 4054 and decompression of resilient rim 4018, as indicated byarrows 4056.

It is a particular feature of the construction of articulation portion3903 and of bone engagement portion 3905 that the application of force3936 does not cause significant deformation of the geometry ofarticulation surface 3902.

Similarly, it is a particular feature of the construction ofarticulation portion 4003 and of bone engagement portion 4005 that theapplication of force 3936 does not cause significant deformation of thegeometry of articulation surface 4002.

It is an additional particular feature of the construction ofarticulation portion 3903 and of bone engagement portion 3905 that wearor deformation of the articulation surface 3902 may be relatively easilyremedied by “plug-in” snap fit replacement of the articulation portion3903 into engagement with the bone engagement portion 3905, which neednot necessarily be replaced.

Similarly, is an additional particular feature of the construction ofarticulation portion 4003 and of bone engagement portion 4005 that wearor deformation of the articulation surface 4002 may be relatively easilyremedied by “plug-in” snap fit replacement of the articulation portion4003 into engagement with the bone engagement portion 4005, which neednot necessarily be replaced.

It is appreciated that the structures and methodology describedhereinabove with reference to FIGS. 5A-11B are applicable not only tothe medial condyle but also equally to the lateral condyle.

In another preferred embodiment of the present invention, the structuresand methodology described hereinabove with reference to FIGS. 5A-11B areapplicable by employing bone engagement portion 3905 as a “tibia surfaceelement” utilizing the bone side configuration and construction of boneengagement portion 3905 for anchoring it to the tibia and also providinganother configuration on the articulation side of bone engagementportion 3905 for operating in an articulation mode with the femurarticulating surface.

In yet another preferred embodiment of the present invention, thestructures and methodology described hereinabove with reference to FIGS.5A-11B are applicable by employing bone engagement portion 4005 as a“femur surface element” utilizing the bone side configuration andconstruction of bone engagement portion 4005 for anchoring it to thefemur and also providing another configuration on the articulation sideof bone engagement portion 4005 for operating in an articulation modewith the tibia articulating surface.

Reference is now made to FIGS. 60, 61, 62 and 63, which are meshedsectional illustrations of the first, second, third and fourth (final)stages in press fit and snap fit installation of an implantableartificial socket 5400, of a similar type to implantable artificialsockets 1100 shown hereinabove in FIG. 1 and/or 1200 shown hereinabovein FIG. 2 and/or 2100 shown hereinabove in FIG. 3 and/or 2200 shownhereinabove in FIG. 4 or similar types, in a machined acetabulum 5420 inaccordance with a preferred embodiment of the present invention whereinsnap fit and press fit engagement situation with the machined acetabulumthe dimensions and configuration of one or both of the implantableartificial socket 5400 and the machined acetabulum 5420 are such thatboth snap fit and press fit engagement are provided.

As seen in FIG. 60 in the first stage in press fit and snap fitinstallation of an implantable artificial socket 5400 in a machinedacetabulum 5420 a surgeon, preferably using his fingers, gentlyintroduces the artificial acetabulum socket into position machinedacetabulum. At the positioning stage shown in FIG. 60, there is providedan implantable artificial socket 5400 having an annular outwardlyextending protrusion 5406, which lies in touching, generallynon-compressive engagement with an annular portion 5410 of a generallyspherical inner concave surface 5412 of a machined acetabulum 5420.Annular portion 5410 lies above a groove 5416, formed in generallyspherical inner concave surface 5412, which is designed to receiveprotrusion 5406. Accordingly, engagement of protrusion 5406 with annularportion 5410 causes the implantable artificial acetabulum socket 5400 torest at a position wherein an outer edge thereof, designated byreference numeral 5430 lies above a corresponding outer edge 5432 ofmachined acetabulum 5420. The separation between the planes of outeredge 5430 of implantable artificial acetabulum socket 5400 and of outeredge 5432 along their mutual axis of symmetry 5440 is indicated byarrows 5444.

As can be seen at the positioning stage shown in FIG. 60, which is thefirst step of the snap fit and press fit engagement, from aconsideration of the meshed sectional illustration of FIG. 60,substantially no stress is applied to the implantable artificialacetabulum socket 5400 and to machined acetabulum 5420 by the engagementthereof.

Reference is now made to FIG. 61, which is a meshed sectionalillustration corresponding the second step of the snap fit and press fitengagement following placement of implantable artificial acetabulumsocket into position as described hereinabove with reference to FIG. 60.At this second step the surgeon, preferably using his fingers, gentlyengages the artificial acetabulum socket 5400 preferably at locations,designated in FIG. 61 by reference numeral 5450 on inner concave surface5511 thereof and presses thereon in a direction indicated by arrows5452, which direction lies generally along axis 5440.

As seen in FIG. 61, the application of this pressure causes displacementof artificial acetabulum socket 5400 in direction 5452. Due to theconcave configuration of surface 5412 at annular surface portion 5410,this displacement produces radially inward compression of artificialacetabulum socket 5400 at protrusion 5406, as indicated by arrows 5454.This radially inward compression results in deformation of theartificial acetabulum socket 5400 at protrusion 5406 and in the generalregion thereof, as indicated, inter alia by arrows 5456.

The racially inward compression and the resulting deformation ofartificial acetabulum socket 5400 produces stresses in the acetabulumsocket 5400, as illustrated, inter alia, by stress contour lines 5461,5462, 5463 and 5464. The above-described engagement of artificialacetabulum socket 5400 with the machined acetabulum 5420 causes forcesto be applied to the machined acetabulum 5420, producing compressionstresses therein, as illustrated, inter alia, by stress contour lines5471, 5472, 5473 and 5474 in a region designated by reference numeral5476, in the vicinity of annular surface portion 5410. It is appreciatedthat the stresses thus produced in machined acetabulum socket 5420produce corresponding strains therein. Both the stresses and the strainshave positive medical implications, as will be discussed hereinbelow.

Displacement of artificial acetabulum socket 5400 in direction 5452 isseen to reduce the separation between the planes of outer edge 5430 ofimplantable artificial acetabulum socket 5400 and of outer edge 5432along axis 5440, indicated by arrows 5484.

Reference is now made to FIG. 62, which is a meshed sectionalillustration corresponding to the third step of the snap fit and pressfit engagement following second step as described hereinabove withreference to FIG. 61. At this stage the surgeon, preferably using hisfingers, presses further on the artificial acetabulum socket 5400preferably at locations, designated by reference numeral 5450 on innerconcave surface 5411 thereof in the direction indicated by arrows 5452.

As seen in FIG. 62, the application of this further pressure, causesfurther displacement of artificial acetabulum socket 5400 in direction5452. This further displacement produces sliding pressure engagementbetween underlying surface portion 5490 of protrusion 5406 at theundercut 5492 and a radially outward extending surface portion 5494 ofgroove 5416. It is noted that the resiliency of the artificialacetabulum socket 5400 causes radially outward displacement ofprotrusion 5406, as indicated by arrows 5496. The resulting radiallyoutward decompression results in different deformation of the artificialacetabulum socket 5400 at protrusion 5406 and in the general regionthereof, as indicated, inter alia by arrows 5498.

This results in reduced and changed stress patterns in both theartificial acetabulum socket 5400 and in the machined acetabulum 5420 atregion 5500 thereof, as indicating by stress contour lines 5511, 5512,5513 and 5514 in artificial acetabulum socket 5400 and by stress contourlines 5521, 5522, 5523 and 5524 in machined acetabulum 5420.

The further displacement of artificial acetabulum socket 5400 indirection 5452 is seen to further reduce the separation between theplanes of outer edge 5430 of implantable artificial acetabulum socket5400 and of outer edge 5432 along axis 5440, indicated by arrows 5534.

Reference is now made to FIG. 63, which is a meshed sectionalillustration corresponding to the fourth and final step of the snap fitand press fit engagement following third step as described hereinabovewith reference to FIG. 62. At this stage the surgeon, preferably usinghis fingers, now presses on the artificial acetabulum socket 5400preferably at locations, designated by reference numeral 5550 on edges5430 thereof in the direction indicated by arrows 5452.

As seen in FIG. 63, the application of this further pressure, causesfurther displacement of artificial acetabulum socket 5400 in direction5452. This further displacement produces sliding snap fit and press fitengagement between protrusion 5406 and groove 5416.

It is noted that the resiliency of the artificial acetabulum socket 5400causes radially outward displacement of protrusion 5406, as indicated byarrows 5552. The resulting radially outward decompression generallyeliminates deformation of the artificial acetabulum socket 5400 atprotrusion 5406 and in the general region thereof designated byreference numeral 5450.

It is noted that the snap fit and press fit engagement shown in FIG. 63produces pressure engagement between concave surface 5412 of themachined acetabulum 5420 and the convex facing surface 5560 ofartificial acetabulum socket 5400, generally along the entire extentthereof. Accordingly the stresses in both the acetabulum socket 5400 andin the machined acetabulum 5420 are generally greater and are notlocalized in the region of the snap fit engagement therebetween orlimited to that region as indicated by stress contour lines 5571, 5572,5573, 5574 and 5575 in artificial acetabulum socket 5400 and by stresscontour lines 5581, 5582, 5583, 5584 and 5585 in acetabulum 5420.

It is also appreciated that the snap fit and press fit engagement of theartificial acetabulum socket 5400 with the machined acetabulum 5420produces locking of the artificial acetabulum socket 5400 in groove5416, wherein undercut 5492 prevents disengagement of protrusion 5406from groove 5416.

It is known in the art that “bone adaptation is likely to be responsiveto a range of factors that constitute the “load history” such as strainmagnitude, cycle number, frequency etc. Such adaptive response hasrecently been proposed as being over the short term. With regards thelong term “load history” it is hypothesized that bone response tostrains within a certain range induce bone modeling and remodelling butthat such activity is followed by a quiescent period. It has also beensuggested that bone has memory and will adapt to previous stimuli. Thusit can be stated that bone adaptation is both spatially and temporallyregulated, by a small subset of the “loading history” and that frequencymay be more important than magnitude, whereby high rates of loadingresult in an increase in interfacial stiffness with an implant, by meansof bone remodelling and an overall increase in bone mass. The influenceof increased stiffness on fluid movement within cannaliculi will furtheralter the stimulation of osteocytes which in turn impact upon the relaymechanism for load bearing stimuli.” From publication Journal ofProsthetic Dentistry—Vol. 81 No. 5 pp 553-561 “Toward an understandingof implant occlusion and strain adaptive bone modeling and remodeling”by Stanford C.-Brand R. May 1999.

It is further known in the art that species such as humans, eagles,sharks and tigers all model and remodel their bones to configuration andsize for sustaining close to exactly the same strain in their bonesubstance when engaged in their normal physical activity.

It is further known in the art that bone remodeling mechanism is afunction of mechanical & environmental conditions wherein cellssubjected to specific mechanical and environmental conditions wouldtransform into a specific type of bone tissue for example as a functionof micro strain ranges. At a first active strain range no cell growthoccurs and at a second active strain range cancellous cell growth occursand at a third active strain range cartilage cell growth occurs and at afourth active strain range cortical cell growth occurs and at a fifthactive strain range irreversible damage of bone occurs, as published byBinderman I et al: Calcified Tissue International 1988; 42: 261-267;

It is further known in the art that cells subjected to compression andlow oxygen tensions would develop into chondroblasts and cartilage andthat cells subjected to constant compressive stresses [hydrostaticstress] inhibit endochondral ossification=>Cartilage and that cellssubjected to compressive hydrostatic pressures greater than about 0.15MPa and strains less than about 15% stimulate enchondral ossification,as published by Yasui N et al: J Bone Joint Surg 1997; 79B: 824-830;

As illustrated in FIG. 63 the stress fields produced for a situationwhere the dimensions and configuration of one or both of the implantableartificial socket 5400 and the machined acetabulum 5420 of a patient aresuch that both snap fit and press fit engagement are provided. Thestress fields produced by the snap fit and press fit engagement areshown distributed within the substance of implantable artificial socket5400 and within certain regions of the substance of the bone ofacetabulum 5420.

As will be discussed hereinbelow in FIGS. 75A, 75B, 76A, 76B; 77A, 77B,78A and 78B additional stress fields may be superimposed onto the stressfields produced by the snap fit and press fit engagement by externalloading exerted on an artificial hip joint constructed and operative inaccordance with a preferred embodiment of the present inventionresulting combined stress fields produced by both the external loads andthe stresses produced by the snap fit and press fit installation of animplantable artificial socket 5420 operative as a component of said hipjoint.

It is further appreciated that the implants of the present invention areconstructed to control the stress and strain distribution at thebone-implant interface, and within the substance of the surroundingbone, resulting in a positive bone remodeling, creating a mechanicalenvironment with conditions that initiate net remodeling activitygrowing new bone cells of structural characteristics. As describedhereinbelow the implants of the present invention are constructed tocontrol the strain distribution by targeting specific locations withinthe bone substance to be subjected to desired strain.

In accordance with preferred embodiments of the present invention,artificial sockets such as implantable artificial socket 5420, as wellas other prostheses described in embodiments of this invention, anycombination of the design parameter grouped in following parenthesis(design loading on the prostheses described in this invention; and theconfiguration and construction of the prostheses described in thisinvention; and of the mechanical properties of the bio stable and biocompatible pliable material from which the prostheses are formeddescribed in this invention; and of insertedly molded in the prosthesesof deformation control elements described in this invention) andemployed by persons skilled in the art produce desired controlleddeformations within the prosthesis. Under these combined conditionsdesired controlled deformations produced within the prosthesis substanceare associated with the transmission of compression stress of desiredmagnitude distributed in desired region within the prosthesis.

It is appreciated by persons skilled in the art that with the stressfields shown in FIG. 63 there are also associated strain fields. It isfor purpose of clarity only that only one type of field is shown in FIG.63, and in other embodiments described in this invention, as is the casealso in descriptions of the entirety of the embodiments of thisinvention while associated strain fields are known to exist where stressfields do exist but are not specifically shown.

It is a particular feature of the construction of the pliable implantsdescribed in this invention that loading exerted on an implant at aspecific location results in deformations and compression stress fieldsin a number of regions of the implant including regions remote from theloading application region.

This feature is partially comparable in principle (for furtherclarification only) to fluid behavior as in terms of hydrostaticpressure distribution generated by pressurized fluid within a container(rigid or flexible) and wherein the outer surfaces of the prosthesis arecomparable to the walls of said example pressurized container andwherein the pressure distribution within an implant substance differsfrom said example by not being uniform in the manner found in apressurized vessel. When example container is by further example of aflexible construction such as in a water bed, the loading by a person'sweight lying on the bed results in uniform pressure remote from thelying person's location. This feature is further compared (for furtherclarification only) in principle to fluid behavior as in terms of flowwithin conduits. Said example fluid flow is influenced by adequate crosssection of the example conduit which effects effortlessness of fluidflow or by sharp turns and by locally narrowed passageways which hinderthe flow in the conduit.

In actual implant configuration there is also provided in accordancewith preferred embodiments described in this invention adequatethickness of the implants (which are the parallel to the conduit crosssection example) and there are also avoided sharp geometrical turns andfolds and locally narrowed thickness (which are compared to theimpediments caused by sharp turns and locally narrowed passageways whichhamper the flow in the example conduit) and thus optimal control isachieved of deformations and compression stress field in desired regionsof the implant including regions remote from the loading applicationregion and which further exert, as described hereinabove, desired strainfor effecting positive bone adaptation in response to said exerted loadon the implant.

As seen hereinabove in FIGS. 60, 61, 62 and 63 implantable artificialsocket 5400, is installed in a machined acetabulum 5420 in accordancewith a preferred embodiment of the present invention wherein both snapfit and press fit engagement are provided for the socket 5400 with themachined acetabulum 5420 producing mechanical locking fixation of theartificial acetabulum socket 5400 in groove 5416, wherein undercut 5492prevents disengagement of protrusion 5406 from groove 5416.

It is known in the art that in the vicinity of rigid implants, such asmetal implants, there are regions of stress shielding in some parts ofthe bone, meaning that such rigid implants take load formerlytransferred to the bone, thereby shielding the bone from the load andcausing bone resorption. Bone resorption results in remodeling the bonegeometry which is the cause in many cases to implant loosening. Thisprocess has been observed in regions such as in the proximal medial boneafter hip replacement, and such as under the tibial component of kneereplacements.

Avoidance of bone resorption and deterioration and loss of bone geometryresponsible for sustaining the long term effectiveness of the mechanicallocking fixation of the artificial acetabulum socket 5400 is broughtabout by the implant strain control in accordance with this inventiondescribed hereinabove and more specific by the targeting of specificlocations within the bone substance to be subjected to desired strain asis taught to promote bone regeneration and strengthening as detailed inbibliography known in the art cited hereinabove as opposed to the boneresorption and deterioration phenomena common in prior art devices.

It is noted that the snap fit and press fit engagement shown in FIG. 63produces pressure engagement between concave surface 5412 of themachined acetabulum 5420 and the convex facing surface 5560 ofartificial acetabulum socket 5400, generally along the entire extentthereof. Accordingly the stresses in both the acetabulum socket 5400 andin the machined acetabulum 5420 are generally greater and are notlocalized in the region of the snap fit engagement therebetween orlimited to that region as indicated by stress contour lines 5571, 5572,5573, 5574 and 5575 in artificial acetabulum socket 5400 and by stresscontour lines 5581, 5582, 5583, 5584 and 5585 in acetabulum 5420.

As seen hereinabove in FIGS. 60, 61, 62 and 63 implantable artificialsocket 5400, of a similar type to implantable artificial sockets 1100shown hereinabove in FIG. 1 and/or 1200 shown hereinabove in FIG. 2and/or 2100 shown hereinabove in FIG. 3 and/or 2200 shown hereinabove inFIG. 4 or similar types are installed in a machined acetabulum 5420 inaccordance with a preferred embodiment of the present invention.

In another preferred embodiment of the present invention implantableartificial socket 5400 is of type wherein the convex bone engagementsurface is preferably configured with a partial configuration pattern ona very limited area of the convex bone engagement surface, oralternatively in another preferred embodiment of the present inventionimplantable artificial socket 5400 is of type wherein the convex boneengagement surface is preferably not configured with any configurationpattern. Such embodiments of the present invention are particularlysuitable for patients with limited mobility and who are only capable oflow level of activity. For this type of patient the stress fieldsproduced for a situation of wherein both snap fit and press fitengagement are provided as illustrated hereinabove in FIG. 63 aresustained for most of the patient's life and wherein no significantsuperimposed stresses exerted by external load resulting from thepatient's level of activity are superimposed for any considerableperiods of time of the patient's life. This is the case of patients withlimited mobility and who are only capable of low level of activity.

Reference is now made to FIGS. 64A and 64B are respective pictorial andpartially cut away illustrations of a bone engaging interface of animplantable tooth implant assembly constructed and operative inaccordance with a preferred embodiment of the present invention; whichis particularly suitable for use in a dental fixture and as anartificial periodontal ligament replacement.

As seen in FIGS. 64A and 64B, a bone engaging interface of animplantable dental implant, designated by reference numeral 5750, isformed preferably by injection molding of polyurethane. Preferredpolyurethane materials are described hereinbelow.

Preferably, bone engaging interface of an implantable tooth implantassembly 5750 is of generally uniform thickness, is symmetric about anaxis 5751 and defines a concave inner fixture anchoring surface 5752,having a beveled edge 5753, and there is also provided on fixtureanchoring surface 5752 a recess 5754 matched with a protrusion 5662provide on a fixture 5660 for snap fit engagement with bone engaginginterface of an implantable tooth implant assembly fixture designated byreference numeral 5660. Bone engaging interface of an implantable toothimplant assembly 5750 has a generally convex outer bone engagementsurface 5754 which preferably has formed thereon at any suitablelocation between its apex and its rim at least one generally annularoutwardly extending protrusion 5756, preferably defining a generallyannular undercut 5758. Alternatively, the protrusion 5756 may be anyother suitable non-annular, open or closed, generally peripheralprotrusion. The protrusion 5756 is preferably arranged for snap fitengagement with a corresponding groove formed by machining of a jawbone.

There is also provided in accordance with a preferred embodiment of thepresent invention a method for implanting a peripheral and continuousrecess (not shown) between the protrusion 5756 and the rim of boneengaging interface of an implantable tooth implant assembly 5750. Thebone remodeling process described hereinabove results in the migrationof bone cells into said peripheral and continuous recess and thuscreates a peripheral continuous seal operative as a barrier separatingthe germ filled oral cavity from the sterile bone and blood supplyunderneath.

Preferably, the protrusion 5756 has a cross-sectional configuration,which is characterized in that an underlying surface portion 5760 ofprotrusion 5756, at the undercut 5758, defines a slope which is sharperthan a corresponding slope of an overlying surface portion 5762 ofprotrusion 5756.

It is a particular feature of the bone engaging interface of animplantable tooth implant assembly 5750 that it is constructed from asingle layer, preferably, molded of a polyurethane of durometer number80 shore A, and includes an inserted internal deformation controlelement 5776, illustrated pictorially in FIG. 64B. The deformationcontrol element 5776 is preferably constructed of a rigid material suchas metal or composite material. Preferably control element 5776 ismolded of a relatively rigid polyurethane, typically one having a Shorehardness of approximately 70D, and may have carbon whiskers embeddedtherein. Alternatively the deformation control element 5776 ispreferably formed of woven high performance fibers such as carbonfibers, KEVLAR®, DYNEEMA®, and glass fibers.

Preferably, deformation control element 5776 is configured andinsertably positioned within bone engaging interface of an implantabletooth implant assembly 5750 with portions of PU material of the singlemolded layer covering it outwardly, inwardly and towards the rim of boneengaging interface of an implantable tooth implant assembly 5750.

The deformation control element 5776 preferably has an overall generallyannular configuration defined by a web portion 5782, a first thickenedportion 5784, having a circular cross section, and a second thickenedportion 5786, having a circular cross section. Deformation controlelement 5776 is further defined by rectangular cut-outs 5792 separatedby flaps 5794 which terminate in thickened portions 5784 which are alsoseparated by cut-outs 5792. Alternatively first thickened portion 5784and second thickened portion 5786 having a non circular cross section.

In another preferred embodiment of the present invention bone engaginginterface of an implantable tooth implant assembly 5750 is preferablyincorporating a reinforcement 5798 constructed of high performancefibers such as carbon fibers, Kevlar®, Dyneema®, and glass fibers. Boneengaging interface of an implantable tooth implant assembly 5750reinforced by fiber reinforcement 5798 imitates the function of theperiodontal ligament which is constructed in nature with structuralfiber tissue and which encapsulate a natural tooth.

It is a particular feature of the configuration and construction of boneengaging interface of an implantable tooth implant assembly 5750according to the principle detailed hereinabove (for furtherclarification only) to enable fluid flow within conduits, providingadequate cross section avoiding sharp turns and locally narrowed“passageways” which hinder transforming deformation and compressionstresses to various portions of bone engaging interface of animplantable tooth implant assembly 5750. This construction andconfiguration of bone engaging interface 5750 ensure also that theplacing therein of fiber reinforcement 5798 is done in a continuousorientation wherein individual fibers and woven fibers are not bent insharp turn or sharply warped. Continuity of reinforcement fibers allowssaid fibers to function optimally in tension.

In another preferred embodiment of the present invention, bone engaginginterface of an implantable tooth implant assembly 5750 is configuredand constructed from material layers and reinforcement, providing shockabsorbing characteristics, allowing a small amount of movement of thetooth in response to moments and forces and impacts of the three phasesof the masticatory cycle (chewing): the preparatory phase and thecrushing phase and the gliding (grinding) phase. Even though shockabsorbing is the most important role of the natural periodontal ligamentit is removed during operation which caused stress concentration andmicro-fractures in alveolar bone.

It is appreciated that the present invention resolve problems associatedwith the removal of the periodontal ligament in operation. Withoutperiodontal dental implant lacks the sensory advantages of a naturaltooth. The dental implant is unable to adapt to occlusal traumaresulting trauma in microfractures of the crestal bone and boneresorption, and chronic screw loosening of the screw-retainedprosthesis, porcelain fracture, unseating of attachments, excessiveocclusal wear, denture sores, purulence, redness, swelling and patientdiscomfort.

Bone engaging interface 5750 replaces the periodontal ligament and isconstructed and operational for replacing the lost shock absorbingfunction of the periodontal ligament and restores natural capabilitiesof a natural healthy tooth.

In accordance with another preferred embodiment of the present inventionthe relationship between the form and the dimensions of bone engaginginterface of an implantable tooth implant assembly 5750 and theprotrusion 5760 are, with respect to the form and the dimensions of thecorresponding machined jaw bone, preferably arranged for press fit andsnap fit engagement with the jaw bone. The press fit feature istypically provided by making the outer dimensions of bone engaginginterface 5750 slightly larger than the corresponding dimensions of themachined jaw bone surface onto which the interface fits.

The convex bone engagement surface 5754 is preferably configured with apattern 5600 preferably defined by a plurality of multidirectionalgenerally radially extending elongate recesses 5614. Recesses 5614 aredefined by wall surfaces 5616 and a bottom surface 5620. In accordancewith a preferred embodiment of the present invention, recesses 5614 areconfigured with wall surfaces 5616 being inclined outwardly toward thebottom surface 5620, creating an undercut configuration having arelatively wider cross sectional dimension near the bottom surface and arelatively narrower cross sectional dimension away from the bottomsurface.

It is a particular feature of the embodiment of FIG. 64A that when boneengaging interface of an implantable tooth implant assembly 5750equipped with implantable dental implant fixture designated by referencenumeral 5660 experiences forces and/or impacts, such as those having acyclic nature resulting from the masticatory cycle, the resultingstresses and strains exerted within the jaw bone in proximity to thebone engagement surface 5754 induce growth of new bone cells, which,gradually, over time, migrate into the recesses 5614. The new bone cellstypically press on other cells, creating remodeling of the bone inengagement with bone engagement surface 5754, causing the bone tomigrate into the channels 5614 gradually, over time, and thus create anundercut locking engagement with the interface 5750. Same processcausing bone to migrate into the peripheral and continuous recessmentioned hereinabove and thus create a peripheral continuous sealoperative as a barrier separating the germ filled oral cavity from thesterile bone and blood supply underneath.

In accordance with another preferred embodiment of the presentinvention, the convex bone engagement surface 5775 is preferablyconfigured with a configuration pattern similar to any configurationpattern such as configuration pattern as shown in FIGS. 1-5.

In accordance with yet another preferred embodiment of the presentinvention, the generally annular outwardly extending protrusion 5760 ispreferably configured with a configuration pattern similar to theconfiguration pattern 5600 or configured with a pattern made of patternsegments similar to the configuration pattern 5600.

Still further in accordance with a preferred embodiment of the presentinvention, preferably at least two ridge elements 5632 are integrallyformed with rim 5630 of bone engaging interface of an implantable toothimplant assembly 5750. The grip element 5630 preferably has an overallgenerally segmented or continuous annular configuration. Grip element5630 is shown in FIG. 64A as a segmented annular configuration definedby a web portion 5634 and thickened portion 5636. Grip ridge elements5632 are constructed operatively in accordance with still anotherpreferred embodiment of the present invention as described in FIGS. 65Aand B hereinbelow to be gripped by the jaws of an implanter tool whichmay be provided for the surgeon to perform the implanting of implantabletooth implant assembly 5650.

FIG. 65A is a sectional illustrations of an implantable tooth implantassembly 5650 mounted onto a jaw 5661 bone and FIG. 65B is a sectionalillustrations of an implantable tooth implant assembly 5651 mounted ontoa jaw bone 5661 in accordance with a preferred embodiments of thepresent invention; constructed and operative in accordance with apreferred embodiment of the present invention and which is particularlyuseful for shock absorbing and sealed fixation to the jaw bone.

In accordance with a preferred embodiment of the present invention asseen in FIG. 65A dental crown prosthesis 5654 is mounted on crownabutment 5658 preferably constructed from a shock absorbing material andoperative in accordance with a preferred embodiment of the presentinvention as a shock absorber for crown prosthesis 5654. Crown abutment5658 is fixed into fixture designated by numeral 5660. Fixture 5660 isfixed into bone engaging interface of an implantable tooth implantassembly 5750 detailed in FIGS. 64A and B.

Preferably in accordance with a preferred embodiment of the presentinvention, dental crown prosthesis 5654 is formed with a mounting cavityhaving an abutment engaging surface 5664 formed with a generally annularinwardly extending protrusion 5668. In accordance with a preferredembodiment of the present invention dental crown prosthesis 5654 is snapfitted onto crown abutment 5658 wherein a protrusion element 5668 issnap fitted onto a matching recess 5670 formed on crown abutment 5658engaging surface.

In accordance with a preferred embodiment of the present invention crownabutment 5658 is fixed into fixture designated by numeral 5660, oralternatively snap fitted onto bone engaging interface, or alternativelysnap fitted and press fitted onto bone engaging interface, oralternatively is mounted onto bone engaging interface by a bayonet-typeconnection, or alternatively screwed onto bone engaging interface andwherein threaded configuration is provided on matching engagementsurfaces of both crown abutment 5658 and Fixture 5660.

In accordance with a preferred embodiment of the present inventionfixture 5660 is press fitted onto bone engaging interface, oralternatively snap fitted onto bone engaging interface, or alternativelysnap fitted and press fitted onto bone engaging interface, oralternatively is mounted onto bone engaging interface by a bayonet-typeconnection, or alternatively screwed onto bone engaging interface andwherein threaded configuration is provided on matching engagementsurfaces of both crown abutment 5658 and bone engaging interface 5750.

In accordance with a preferred embodiment of the present invention asseen in FIG. 65B crown abutment 5659 is directly fixed into boneengaging interface of an implantable tooth implant assembly 5750 withoutan intermediary element such as fixture 5660. In accordance with apreferred embodiment of the present invention crown abutment 5658 ispress fitted onto bone engaging interface, or alternatively snap fittedonto bone engaging interface, or alternatively snap fitted and pressfitted onto bone engaging interface, or alternatively is mounted ontobone engaging interface by a bayonet-type connection, or alternativelyscrewed onto bone engaging interface and wherein threaded configurationis provided on matching engagement surfaces of both crown abutment 5658and bone engaging interface 5750.

Still further in accordance with a preferred embodiment of the presentinvention, implantable tooth implant assembly 5650 is preferablyimplanted into a jaw bone by an implanter tool which is constructed andoperative for performing the surgery by simpler and reduced number ofstages of the operation. Grip ridge elements 5632 of bone engaginginterface of an implantable tooth implant assembly 5750 are constructedoperatively are constructed and operative in accordance with stillanother preferred embodiment of the present invention to be gripped bythe jaws of an implanter tool which may be provided for the surgeon toperform the implanting of implantable dental implant 5600 or 5601simultaneously with the bone engaging interface 5750 in one smootheasy-to-perform installation process. Although implanter tool suitableto operate in conjunction with grip ridge element 5632 is not shown, itsfunction utilizing grip ridge element 5632 and the pliability of theinterface 5750 is described hereinbelow.

In accordance with a preferred embodiment of the present inventionpreferably an implanter tool simultaneously grasps grip ridge elements5632 and exerts stretching forces designated by numerals 5650 resultantof which is along the general direction of axis 5751 operating on ridgeelements 5632 and exerting pushing forces designated by numerals 5652resultant of which is along the general direction of axis 5751,operating on concave inner fixture anchoring surface 5752 bone engaginginterface of an implantable tooth implant assembly 5750.

The simultaneous pushing forces 5652 operating on concave inner fixtureanchoring surface 5752 are being exerted directly by an element of theimplanter tool or alternatively by fixture 5660 as seen in FIG. 65A, oralternatively by crown abutment 5658 as seen in FIG. 65B and wherein anyof elements of the implanter tool or fixture 5660 or crown abutment 5658are placed inside bone engaging interface 5750 and grasped by theimplanter tool. The simultaneous stretching and pushing operationstretches bone engaging interface of an implantable tooth implantassembly 5750 and allows easy insertion into the machined jaw bonefollowing the simultaneous stretching and pushing operation.

In accordance with a preferred embodiment of the present invention, asurgeon using an implanter tool inserts into a suitably machined jawbone the train comprised of implanter tool and a combination of elementsof implantable tooth implant assembly 5650 and positioned forimplanting. Following the placing described hereinabove the surgeonproceeds to operate the implanter to continuously change flexing andpushing forces until the implantable tooth implant assembly 5650 orassembly 5651 is properly installed by press fit onto bone engaginginterface, or alternatively snap fitted onto bone engaging interface, oralternatively snap fitted and press fitted onto bone engaging interface.

Still further in accordance with a preferred embodiment of the presentinvention, preferably grip ridge elements such as grip ridge elements5632 shown in FIG. 64A are formed and operative with an implanter toolas described hereinabove on any of implantable artificial sockets 5400shown in FIGS. 60 61 62 and 63, and implantable artificial sockets 1100shown hereinabove in FIG. 1 and socket 1200 shown hereinabove in FIG. 2and socket 2100 shown hereinabove in FIG. 3 and sockets 2200 shownhereinabove in FIG. 4.

In accordance with a preferred embodiment of the present invention, asurgeon using an implanter tool implants into a suitably machinedacetabulum bone the train comprised of implanter tool and any of socket5400 shown in FIGS. 60 61 62 and 63, and implantable artificial sockets1100 shown hereinabove in FIG. 1 and socket 1200 shown hereinabove inFIG. 2 and socket 2100 shown hereinabove in FIG. 3 and sockets 2200shown hereinabove in FIG. 4 implanting any of said devices by press fitonto bone engaging interface, or alternatively snap fitted onto boneengaging interface, or alternatively snap fitted and press fitted ontobone engaging interface.

Reference is now made to FIG. 66 which is a partially cut awayillustration of a bone engaging interface integrally formed with a gumembankment element of an implantable tooth implant assembly implanted ina suitable machined jaw bone 5684 constructed and operative inaccordance with a preferred embodiment of the present invention; whichis particularly suitable for use in a dental fixture and as anartificial periodontal ligament replacement.

As seen in FIG. 66 a bone engaging interface of an implantable dentalimplant, designated by reference numeral 5674 is configured andconstructed similar to bone engaging interface 5750 as shown in FIG. 64Aand extended therefrom outwardly and upwardly from rim 5678 a flexiblegum embankment element 5680 constructed and operative to protect the gum5682 following a surgery.

It is further appreciated that in preferred embodiments of implantsdescribed in FIGS. 64A, 64B, 65A, 65B and 66 hereinabove implants may beconstructed with any of the following: Where the material of the boneinterface element being more flexible than that of bone; Where boneinterface element is shock-absorbing; and wherein bone interface hasmechanical properties of mammalian cartilage; Where bone interface ismore resilient that the jaw bone;

Where the abutment is formed with a plurality of portions havingdifferent mechanical properties; Where abutment comprises an outer shelland an inner core; wherein said artificial abutment is formed with aplurality of alternating adjacent first and second portions, said firstportions being generally more rigid than said second portions andwherein bone-interface comprises at least two layers;

Reference is now made to FIGS. 74A, 75B, 75A, 75B, 76A, 76B, 77A, 77B,78A and 78B, which are simplified meshed sectional illustrations of anartificial hip joint constructed and operative in accordance withpreferred embodiments of the present invention, showing stress fieldsand associated strain fields produced and the force distributionsproduced by snap fit with press-fit installation of an implantableartificial socket 6100 of the type of implantable artificial socket 5400shown in FIGS. 60, 61, 62 and 63, or of a similar type to implantableartificial sockets 1100 shown hereinabove in FIG. 1 and/or 1200 shownhereinabove in FIG. 2 and/or 2100 shown hereinabove in FIG. 3 and/or2200 shown hereinabove in FIG. 4 or similar types are installed in amachined acetabulum in a situation where the dimensions andconfiguration of one or both of the implantable artificial socket andthe machined acetabulum are such that both snap-fit and press-fitengagement are provided into a suitably machined natural acetabulum of apatient wherein bone engagement surface of implantable artificial socketengages machined surface of natural acetabulum. In alternativeembodiments of the present invention convex bone engagement surfaces ofartificial sockets described in FIGS. 74A, 75B, 75A, 75B, 76A, 76B, 77A,77B, 78A and 78B hereinbelow are not configured with any configurationpattern.

In accordance with yet another preferred embodiment of the presentinvention convex bone engagement surfaces of artificial socketsdescribed in FIGS. 74A, 75B, 75A, 75B, 76A, 76B, 77A, 77B, 78A and 78Bhereinbelow are configured with a configuration pattern.

As described in FIG. 63 hereinabove it is appreciated by persons skilledin the art that with the stress field shown there is also an associatedstrain field and it is for purpose of clarity that only one type offield is shown here and the existed strain field is not shown.

It is a particular feature of the construction of implantable artificialsocket constructed and operative in a hip join environment detailed inFIGS. FIGS. 74A, 75B, 75A, 75B, 76A, 76B, 77A, 77B, 78A and 78Bcontrolling, as is described in FIG. 63 hereinabove, the stress andstrain distribution within the substance of the surrounding bone,resulting in a positive bone remodeling, creating a mechanicalenvironment with conditions that initiate net remodeling activitygrowing new bone cells of structural characteristics and targetingspecific locations within the bone substance to be subjected to desiredstrain.

As illustrated in FIGS. 74A and 74B the stress fields produced and forcedistribution produced in a situation as mentioned hereinabove that bothsnap-fit and press-fit engagement are provided into a suitably machinednatural acetabulum 6102 of a patient wherein bone engagement surface6101 of implantable artificial socket 6100 engages machined surface 6103of natural acetabulum 6102. The stress fields produced by the snap-fitand press-fit engagement are shown distributed within the substance ofimplantable artificial socket 6100 and within substantial regions of thesubstance of the bone of acetabulum 6102 and there exist also associatedstrain fields with in said regions of the substance of the bone ofacetabulum 6102.

As a result an associated strain fields are created within substantialregions of the substance of the bone of acetabulum 6102 with strainmagnitudes comparable to those found in bones of a physically activeperson. Said strain field activate bone growth and bone remodeling insaid regions of the substance of the bone of acetabulum 6102 and enhanceanchoring and adhesion of the prostheses to the bone.

A conventional artificial femoral head 6104 is mounted onto aconventional femoral stem in an orientation whereby an axis of symmetry6112, of implantable artificial socket 6100, and an axis of symmetry6114, of artificial femoral head 6104, are substantially aligned. Aseparation between the planes of outer edge 6122 of implantableartificial acetabulum socket 6100 and of outer edge 6124 of naturalacetabulum 6102 along axis 6112 is created, as indicated by arrows 6126.FIGS. 74A and 74B illustrate a situation wherein the patient is notexerting any external force on the hip joint.

The snap-fit with press-fit installation, illustrated in FIG. 60, FIG.61, FIG. 62 and FIG. 63, produces snap-fit engagement between protrusion6132 and groove 6134, formed in natural acetabulum 6102, with pressureengagement between convex surface 6142 of protrusion 6132 and theconcave surface 6144 of groove 6134. The snap-fit with press-fitinstallation also produces pressure engagement between concave surface6146, of the machined acetabulum 6102, and the convex facing surface6148, of artificial acetabulum socket 6100, generally along the entireextent thereof.

As further illustrated in FIG. 60, FIG. 61, FIG. 62 and FIG. 63, theabove-described engagement of artificial acetabulum socket 6100 with themachined acetabulum 6102 causes deformation of artificial acetabulumsocket 6100 and produces stressing in the acetabulum socket 6100, asillustrated, inter alia, by stress contour lines 6161 and 6162. Thestresses and strains which occur within artificial acetabulum socket6100, and the deformation of socket 6100 which is associated with thesestresses and strains, transfer onto the surface 6146 of the machinedacetabulum 6102 a distributed force pattern 6172, as seen in FIG. 74B.

In accordance with another preferred embodiment of the present inventionthe partially hemispherical convex bone engagement surface of the outerregion 6174 of implantable artificial acetabulum socket 6100 is notconfigured with a configuration pattern and is not engaged by contactwith any part of a bone or any apparatus on its outer surface 6176 sothat outer edge 6122 of outer region 6174 is not constrained and is freeto deform along axis 6112 in the situation of a snap-fit and press-fitengagement as indicated by the separation 6126 of outer edge 6122.

In accordance with yet another preferred embodiment of the presentinvention, the partially hemispherical convex bone engagement surface ofthe outer region 6174 of implantable artificial acetabulum socket 6100is configured with a configuration pattern of types shown hereinabove inFIGS. 1 to 4. Bone remodeling process described hereinabove fixedlyanchors the bone with the configuration pattern configured on thepartially hemispherical convex bone engagement surface of the outerregion 6174. The outer region 6174 of implantable artificial acetabulumsocket 6100 is partially constrained and a reduced deformation occursalong axis 6112 compared to a situation described hereinabove whereinouter region 6174 of implantable artificial acetabulum socket 6100 isnot configured with a configuration pattern and the said decreaseddeformation result in an improved fixation and longevity of implantableartificial acetabulum socket 6100.

As seen in FIG. 74B the distributed force pattern 6172 is characterizedby a peak distributed force regions 6180, a medium distributed forceregion 6181 with distributed forces smaller than those of peak region6180, a reduced force region 6182 and a reduced force region 6183 inproximity to outer region 6174 of natural acetabulum 6102 due to thefreedom of outer region 6174 to deform.

As illustrated in FIGS. 75A and 75B a changed stress fields distributedwithin substantial regions of the bone substance of natural acetabulum6102 and changed force pattern and deformations is resulted from loadingof the joint by force indicated by numerals 6200 with respect to stressfields, distributed force pattern and deformation, as seen in FIGS. 74Aand 74B. As it occurs in the life cycle of the joint loading the loadforce 6200 may be a static loading of a cyclic loading. The significanceof cyclic strain field (resulting from cyclic loading) in bone and theregeneration of bone cells associated with said strain fields aredetailed in FIG. 63 hereinabove. There is no expression in FIGS. 75A and75B to eventual cyclic loading cases however it is appreciated bypersons skilled in the art that the cyclic stress distribution exertedby cyclic load can be understood observing the static stressdistribution as described in FIG. 75B and in 76A, 76B, 77A, 77B, 78A and78B hereinbelow. And it is further understood as detailed in FIG. 63hereinabove that there exist strain fields associated with said stressfields.

When the patient exerts an external force 6200 on the hip joint, theseparation between the planes of outer edge 6122 of implantableartificial acetabulum socket 6100 and of outer edge 6124 of naturalacetabulum 6102 along axis 6112, indicated by arrows 6202, is greaterthan that of separation 6126, shown in FIG. 74A, wherein the patient isnot exerting any external force on the hip joint.

As seen in FIGS. 75A and 75B the combined action of above-describedsnap-fit with press-fit engagement with external force 6200 on the hipjoint produce stresses in the acetabulum socket 6100, as illustrated,inter alia, by stress contour lines 6261, 6262, 6263 and 6264 whichcover larger stressed area compared with those areas in the stressedacetabulum socket 6100, as shown in FIGS. 74A and 74B, and includeregions with larger stresses than produced stresses in the acetabulumsocket 6100, as illustrated, inter alia, by stress contour lines 6161and 6162 as seen in FIG. 74A, and by stress contour lines 6271 and 6272,and 6273 which cover larger stressed area compared to the stressednatural acetabulum 6102, as shown in FIGS. 74A and 74B, and includeregions with larger stresses than produced stresses in the naturalacetabulum 6102, as illustrated, inter alia, by stress contour lines6171 and 6172 as seen in FIG. 74A.

The stresses and strains which occur within artificial acetabulum socket6100 and the deformation of socket 6100 which is associated with thesestresses and strains transfer a distributed force pattern 6272 onto thesurface 6146 of the machined acetabulum 6102, as illustrated in FIG.75B.

The distributed force pattern 6272 is characterized by a reduced forceregion 6282 and a reduced force region 6283 in proximity to outer region6174 of natural acetabulum 6102 due to the freedom of outer region 6174to deform and a first peak force region 6284 and a second peak forceregion 6285 and a trough force region 6286. The distributed forcepattern 6272 is of larger force magnitude that that of distributed forcepattern 6172 shown for comparison as a dotted line in FIG. 75B.

The differences in the distributed force pattern 6272 for a loaded jointversus the force pattern 6172 of an unloaded socket 6100 installed in asnap-fit and press-fit engagement may vary as load 6200 varies. In thecase of a very small load 6200 there will be very small variation offorce patterns 6172 and 6272. This maybe the case for patients withlimited mobility, as described in FIG. 63 hereinabove, and who are onlycapable of low level of activity. Socket 6100 is suitable or this typeof patient very small variation between force patterns 6172 and 6272 aresustained for most of the patient's life and wherein no significantsuperimposed stresses exerted by external load resulting from thepatient's level of activity are superimposed for any considerableperiods of time of the patient's life.

In another preferred embodiment of the present invention implantableartificial socket 6100 is of type wherein the convex bone engagementsurface is preferably configured with a partial configuration pattern ona very limited area of the convex bone engagement surface, oralternatively in another preferred embodiment of the present inventionimplantable artificial socket 5400 is of type wherein the convex boneengagement surface is preferably not configured with any configurationpattern.

As illustrated in FIGS. 76A and 76B a changed stress fields distributedwithin substantial regions of the bone substance of natural acetabulum6402 and changed force pattern and deformations is resulted from loadingof the joint by force indicated by numerals 6400 with respect to stressfields, distributed force pattern and deformation, as seen in FIGS. 75Aand 75B.

FIGS. 76A and 76B show said joint constructed and operative inaccordance with a preferred embodiment of the present invention, andshowing stress fields distributed, force patterns and deformationsresulting from loading of the joint incorporating an implantableartificial socket 6500 which is modified by variations in its thicknessat various locations and/or preferable constructed with at least oneadditional layer. As seen in FIG. 76A artificial socket 6500 isconstructed from three layers showing intermediate layer 6323,performing as a deformation control layer, preferably, molded of apolyurethane of durometer number 70 shore D and preferably, includingcarbon whiskers. Resulting from loading of the joint by force indicatedby numerals 6400 modified stress fields distributed, force patterns anddeformations are shown with respect to stress fields, distributed forcepattern and deformation as seen in FIGS. 75A and 75B, whereinimplantable artificial acetabulum socket 6100 is constructed with eventhickness and of a unitary construction of one layer.

In the situation detailed in FIGS. 76A and 76B, the dimensions andconfiguration of one or both of the implantable artificial socket 6500and the machined acetabulum are such that both snap-fit and press-fitengagement are provided into a suitably machined natural acetabulum 6302of a patient, and a conventional artificial femoral head 6304 is mountedonto a conventional femoral stem in a matching orientation of both axisof symmetry 6112 of implantable artificial socket 6500 and axis ofsymmetry 6314 of artificial femoral head 6304 coincide, and wherein aseparation between the planes of outer edge 6322 of implantableartificial acetabulum socket 6500 and of outer edge 6124 of naturalacetabulum 6102 along axis 6112 is created, as indicated by arrows 6306.

The uneven thickness portion of artificial acetabulum socket 6500comprises a region 6228 of a thickness less than the average thicknessof uneven thickness portion and a region 6230 of a thickness greaterthan the average thickness of uneven thickness portion. This uniqueconfiguration produces variations of the stresses and strains whichoccur within artificial acetabulum socket 6500 and the deformation ofsocket 6500 which is associated with these stresses and strains transferonto the surface 6446 of the machined acetabulum 6402 as a distributedforce pattern 6472, as seen in FIG. 76B, compared to the stresses andstrains which occurs within artificial acetabulum socket 6100 and thedeformation of socket 6100 which is associated with these stresses andstrains transfer onto the surface 6146 of the machined acetabulum 6102detailed in FIG. 75A.

Thickness variations and or multi layer construction of socket 6500produce stress variations in the natural acetabulum 6402 such thatthicker portions of socket 6500 produce higher stress regions andthinner portions of socket 6500 produce lower stress regions.

As seen in FIGS. 76A and 76B, the distributed force pattern 6472 variesfrom distributed force pattern 6272 of FIGS. 75A and 75B, shown in FIG.76B by a dotted line. When compared to distributed force pattern 6272,detailed in FIG. 75B, distributed force pattern 6472 is characterized bya first peak force region 6484 which is lower than that of the peakforce region 6284 of distributed force pattern 6272 due to a lesserstressed region corresponding to the region 6228 of a thickness thinnerthan the average thickness of uneven thickness portion, and a troughforce region 6386 which is larger than and a trough force region 6286 ofdistributed force pattern 6272 due to a lesser stressed regioncorresponding to the region 6230 of a thickness thicker than the averagethickness of uneven thickness portion.

Distributed force pattern 6472 is also characterized by a second peakforce region 6484 which is lower than that of the peak force region 6284of distributed force pattern 6272 and by a reduced force region 6282 anda reduced force region 6283 in proximity to outer region 6174 of naturalacetabulum 6102 due to the freedom of outer region 6174 to deform and afirst peak force region 6284 and a second peak force region 6285.

The uneven thickness socket 6500 results in a distributed force pattern6472, which describes a more even force distribution than that producedby socket 6100 configured of unitary construction with an eventhickness.

As illustrated in FIGS. 77A and 78A a changed stress fields distributedwithin substantial regions of the bone substance of natural acetabulum6502 and changed force pattern and deformations is resulted from loadingof the joint by force indicated by numerals 6601 with respect to stressfields, distributed force pattern and deformation, as seen in FIGS. 76Aand 76B.

FIGS. 77A and 78A show said joint constructed and operative inaccordance with a preferred embodiment of the present invention, andshowing stress fields distributed, force patterns and deformationsresulting from loading of the joint incorporating an implantableartificial socket 6600 which are modified by provision of deformationcontrol element 6526 configured in the implantable artificial socket6600.

In the situation detailed in FIGS. 77A and 78A the dimensions andconfiguration of one or both of the implantable artificial socket 6600and the machined acetabulum are such that both snap-fit and press-fitengagement are provided into a suitably machined natural acetabulum 6502of a patient, and a conventional artificial femoral head 6504 is mountedonto a conventional femoral stem in a matching orientation of both axisof symmetry 6512 of implantable artificial socket 6600 and axis ofsymmetry 6514 of artificial femoral head 6504 coincide, and wherein theseparation between the planes of outer edge 6522 of implantableartificial acetabulum socket 6600 and of outer edge 6524 of naturalacetabulum 6502 along axis 6512, indicated by arrows 6506.

The snap-fit with press-fit installation as seen in FIG. 60, FIG. 61,FIG. 62 and FIG. 63 produces snap-fit locking engagement betweenprotrusion 6132 and groove 6134 formed in natural acetabulum 6502 withpressure engagement between convex surface 4533 of protrusion 4506 andthe concave surface 6544 of groove 6534.

As seen in FIG. 65, a particular feature of the implantable artificialsocket 6600 that it is constructed with deformation control element 6526constructed in a similar manner to deformation control element 5776 inFIG. 64B, preferably, molded of a polyurethane of durometer number 70shore D. Preferably, including carbon wiskers, of carbon woven fabric,or alternatively from other rigid material such as metal, highperformance composite materials and the like. This unique constructionof socket 6600 produces variations of the stresses and strains whichoccurs within artificial acetabulum socket 6600 and the deformation ofsocket 6600 which is associated with these stresses and strains transferonto the surface 6446 of the machined acetabulum 6402 a distributedforce pattern 6472 as seen in FIG. 78A compared to the stresses andstrains which occurs within artificial acetabulum socket 6100 and thedeformation of socket 6100 which is associated with these stresses andstrains transfer onto the surface 6146 of the machined acetabulum 6102detailed in FIG. 75A.

As seen in FIGS. 77A and 78A, the distributed force pattern 6572 variesfrom distributed force pattern 6172 shown in FIG. 75B by a dotted line.Distributed force pattern 6572 is mainly characterized by a reducedforce region 6582 with a higher load than that of reduced force region6282 of distributed force pattern 6272 and by a reduced force region6583 in proximity to outer region 6574 of natural acetabulum 6502 with ahigher load than that of reduced force region 6283 of distributed forcepattern 6272 due to the restricted freedom of outer region 6574 todeform induced by deformation control element 6526. As deformationcontrol element 6526 preferably, molded of a polyurethane of durometernumber 70 shore D. Preferably, including carbon wiskers, of other rigidalternative constructions as detailed above, it is less flexible and itrestrains the deformation of the entire socket 6300 along its tangentialdirection and in particular the deformation of its outer region 6574,first thickened portion 4534 of deformation control element 6526 ispositioned within thickened portion inwards to protrusion 4506 of socket6600. The surrounding molded material within the protrusion 4506 locksthickened portion 4534 from movement with reference to protrusion 4506.Protrusion 4506 is anchored within a matching machined groove 6134formed in natural acetabulum 6502, and thus thickened portion 4534 isretrained from movement with reference to protrusion groove 6134 formedin natural acetabulum 6502.

As can be seen in FIG. 77A, the separation between the planes of outeredge 6522 of implantable artificial acetabulum socket 6600 and of outeredge 6524 of natural acetabulum 6502 along axis 6512, indicated byarrows 6506 is smaller than that of separation 6126 shown in FIG. 75Awherein there is no deformation control element such as deformationcontrol element 6526 in socket 6100 of in socket 6500.

In the embodiments of this invention shown in FIGS. 74A, 75A and 76A theimplantable artificial sockets 6100 or 6500 assembled unto machinednatural acetabulum such as natural acetabulum 6102 are shown with boneengagement surfaces which are not formed with any configuration patternsuch as the hexagonal configuration pattern 1110 shown in FIG. 1hereinabove formed on convex bone engagement surface 1101 or such as thespiral configuration pattern 2110 shown in FIG. 3 hereinabove formed onconvex bone engagement surface 2101 or configuration pattern shown inFIG. 4.

In other preferred embodiments of this invention bone engagementsurfaces implantable artificial sockets 6100 or 6500 may be formed withsuitable configuration patterns such as configuration patterns shown inFIGS. 1 to 4 hereinabove or any other suitable configuration pattern oralternatively may be preferably formed with any other none-smoothsuitable surface textures.

As seen in FIGS. 77A and 77B, the distributed force pattern 6672 variesfrom distributed force pattern 6472 of FIGS. 76A and 76B, shown in FIG.77B by a dotted line. When compared to distributed force pattern 6472,detailed in FIG. 76B, distributed force pattern 6672 is characterized bya more even force distribution than that produced by socket 6500configured of FIG. 76A.

As described FIG. 63 hereinabove the outer surfaces of the prosthesis,as is the case in socket 6600 described in FIG. 77A, are comparable tothe walls of said example pressurized container. Deformation controlelement 6526 operate in a manner a lid on a pressure container operatespreventing pressure to escape from said container. In a similar mannerDeformation control element 6526 prevent outward deformation to occurand thus seal the compression stresses within the outer surfaces ofsocket 6600.

As illustrated in FIGS. 78A and 78B the stress fields produced and forcedistribution produced in a situation wherein a snap-fit or both snap-fitand press-fit engagement of femoral head surface element 7200 areprovided into a suitably machined natural femoral head 7100 and whereina snap-fit or both snap-fit and press-fit engagement of a socket 7202are provided into a suitably machined natural acetabulum 7102 of apatient operative in a hip joint environment and loaded by force 7000.

The stress fields produced due to loading 7000 by the engagement of bothimplants to respective bones are shown distributed within the substanceof implants and artificial socket 7102 and femoral head 7100 and thereexist also associated strain fields with in said regions of thesubstance of the femoral bone and the acetabulum bone. Femoral headsurface element 7200 may be constructed in similar constructions of anyof the implants shown hereinabove and in particular include deformationcontrol element 7526.

It is a particular feature of the construction of implantable femoralhead surface element 7200 constructed and operative in a hip joinenvironment detailed in FIG. 78A controlling, as is described in FIG. 63hereinabove, the stress and strain distribution within the substance ofthe surrounding femoral head bone, resulting in a positive boneremodeling, creating a mechanical environment with conditions thatinitiate net remodeling activity growing new bone cells of structuralcharacteristics and targeting specific locations within the bonesubstance to be subjected to desired strain. The force distributionpattern on femoral head 7100 is designated by numeral 7210 and shown inFIG. 78B.

In accordance with yet another preferred embodiment of the presentinvention the implantable artificial socket for a joint also includes abioactive coating. Preferably, the bioactive coating is formed by gritblasting. Alternatively, the bioactive coating is formed by spraying. Inaccordance with another preferred embodiment, the bioactive coating alsoincludes an elastomer.

In accordance with yet another preferred embodiment of the presentinvention the implantable artificial femoral head resurfacing elementalso includes a bioactive coating. Preferably, the bioactive coating isformed by grit blasting. Alternatively, the bioactive coating is formedby spraying. In accordance with another preferred embodiment, thebioactive coating also includes an elastomer.

The surface roughness and surface porosity is provided preferably byco-spraying of an elastomer and bioactive materials composite coating.The premixed feedstock may be PU/HA (polyurethane/Hydroxylapatite), thusproviding a co-spraying of PU/HA composite coating. The bioactivematerials are preferably hydroxylapatite or any other suitable calciumphosphate-containing materials. These bioactive materials cause thecontact surface of the artificial implantation device to becomebioactive, stimulating bone growth to provide an adhesion of the implantto the bone and accelerate osteointegration.

The feedstock for this coating can be in powder form, where acombination of PU and HA powders are preferably blended in suitableratios and sprayed to form the desired coating. Alternatively, thefeedstock can be a PU rod that is co-sprayed with HA powder particlesthat are fed separately into the molten particle flow. The PU rod canalso be extruded with HA powder mixed within it so that a composite rodfeedstock is obtained. Alternatively, any other suitable method ofcombining the PU and the bioactive materials may be used. The rod willthen be fed directly though the spray device and the resulting coatingwill contain both HA and PU particles forming the desired matrix.

In accordance with a preferred embodiment of the present invention aspraying apparatus is used, as described hereinabove, to modify thecontact surface of the artificial implantation device by coating. Thiscoating is preferably provided using a combustion process, whichutilizes an oxygen-fuel mixture and heats the particles as they are fedthrough a gravity hopper through the center of the spraying apparatus. Anozzle directs the combustion gasses and the molten particles towardsthe contact surface of the artificial implantation device. Thecombustion of the gasses occurs within a chamber in the nozzle and acarrier gas is used to propel the molten particles forward, and preventthem from sticking to the nozzle walls. When using rod feedstock (inplace of powder), atomizing gas is used to break the tip of the moltenrod into discrete particles.

A coating of molten polyurethane particles can be applied to the contactsurface of the artificial implantation device in order to create a roughporous surface into which the bone can grow. The process may start witha preheating step that is designed to melt the surface of the implantand provide for a chemical bond between the surface and the polyurethaneparticles, although the process can be applied to a cold surface aswell. The thickness of the coating can be regulated.

The coating deposited using the above mentioned combustion spray processmay be a Polymer-Hydroxylapatite composite coating. This coating systemconsists of a combination of polyurethane particles that will beco-sprayed with HA powder. The resulting coating will form a polymerscaffold like structure that will entrap the HA particles within. Thiscomposite structure will help anchor the implant by enabling boneattachment to the exposed HA particles and eventually boneinterdigitation in the pores created as the HA resorbs with time.

Alternatively, a coating can be deposited onto the contact surface ofartificial the implantation device by means of dipping, whereby a slurryis made of a polymer material, having a certain quantity of bioactiveparticles mixed within it The artificial implantation device is dippedinto the slurry, after which it is allowed to dry. As the slurry dries,a composite polymer/bioactive material coating is created, where thebioactive particles are trapped within the polymer matrix.

The coating may be an elastomer on elastomer coating, such as apolyurethane on polyurethane coating. The polyurethane coating can havea hardness of 55D and upwards for enhancing bio-stability on the outersurface, while the artificial implantation device and contact surface isof hardness 80A.

In addition to the enhanced bone adhesion methods described herein, thecontact surface of an artificial implantation device may also be treatedusing one of the following Surface Modification processes: Atomiccleaning, adhesion promotion, molecular grafting, cell attachmentenhancement, and Plasma Enhanced Chemical Vapor Deposition (PECVD)coatings, such as implemented by the MetroLine Surface, Inc. Surfacemodification processes improve the articulating properties of thecontact surface by reducing friction and thereby enhance the resistanceto wear.

The following is a brief description of a best mode manufacturingprocess of the implantable artificial socket 1100 shown in FIGS. 1A to1C. The manufacturing process typically comprises the steps as describedhereinbelow. It is appreciated that the steps of the manufacturingprocess are monitored and controlled in order to assure the quality ofthe products meets the required standards.

Step 1. Material Identification:

A preferable material used for manufacturing a cup used for preparingthe implantable artificial socket 1100 is Polycarbonate Urethane Bionate80A, which is supplied by Polymer Technology Group Inc., 2810 7^(th)Street, Berkeley, Calif. 94710, U.S.A.

Step 2. Equipment used for Cup Manufacturing:

Step 2.1. Equipment Use for Pre-Injection Drying:

A desiccant that has the ability to be connected directly to the screwof an injection molding machine and reach 50 deg dew point, ispreferably used.

Step 2.2. Equipment Use for Cup Injection:

The injection molding machine includes computerized data acquisitionability and an 18-20 mm diameter cylinder, for example an ARBURG 4020device.

Step 2.3. Equipment Use for Post-Injection Curing:

Industrial oven capable of maintaining 80° C.±2° C. for approximately 15hours.

Step 3. Preprocess for the Raw Material:

The drying of the raw material is performed using a desiccantdehumidifier, outside of a clean room.

Step 3.1. The Drying Process Typically Includes the Steps:

-   I. 12 hours at 65° C. [−50 dew point]-   II. 4 hours at 93° C. [−50 dew point]

The final product humidity should be preferably between 0.01%-0.02%.

Step 4. The Manufacturing Process:

-   1. Drying of the material for 16 hours by special drier (−50° C.)    desiccant.-   2. Direct transfer of the material in the drier to the injection    machine, i.e. connecting a drier device directly to the machine.-   3. Injection molding.-   4. Curing in an oven for 16 hours.-   5. Packaging.-   6. Sterilization in Gamma.

Preferred polyurethane materials for use in the embodiments describedhereinabove include the following materials.

The following materials are manufactured by POLYMER TECHNOLOGY GROUPPTG.

Bionate® polycarbonate-urethane is among the most extensively testedbiomaterials ever developed. The Polymer Technology Group Incorporatedacquired the license to manufacture this thermoplastic elastomer fromCorvita Corporation (who marketed it under the name Corethane®) in 1996.

Carbonate linkages adjacent to hydrocarbon groups give this family ofmaterials oxidative stability, making these polymers attractive inapplications where oxidation is a potential mode of degradation, such asin pacemaker leads, ventricular assist devices, catheters, stents, andmany other biomedical devices. Polycarbonate urethanes were the firstbiomedical polyurethanes promoted for their biostability.

Bionate® polycarbonate-urethane is a thermoplastic elastomer formed asthe reaction product of a hydroxyl terminated polycarbonate, an aromaticdiisocyanate, and a low molecular weightglycol used as a chain extender.

The scope of Bionate PCUs tests—encompassing Histology, Carcinogenicity,Biostability, and Tripartite Biocompatiblity Guidance for MedicalDevices—reassures medical device and implant manufacturers of thematerial's biocompatibility. This allows biomaterials decision makersthe ability to choose an efficacious biomaterial that will add to thecost-effectiveness of the development of their device or implant Belowis a summary of the extensive biocompatibility testing conducted onBionate PCUs, including its successful completion of a 2-yearcarcinogenicity study.

Copolymers of silicone with poplyurethanes:

PurSil™ Silicone Polyether Urethane

CarboSil™ Silicone Polycarbonate Urethane

Silicones have long been known to be biostable and biocompatible in mostimplants, and also frequently have the low hardness and low modulususeful for many device applications. Conventional silicone elastomerscan have very high ultimate elongations, but only low to moderatetensile strengths. Consequently, the toughness of most biomedicalsilicone elastomers is not particularly high. Another disadvantage ofconventional silicone elastomers in device manufacturing is the need forcross-linking to develop useful properties. Once cross-linked, theresulting thermoset silicone cannot be redissolved or remelted.

In contrast, conventional polyurethane elastomers are generallythermoplastic with excellent physical properties. Thermoplastic urethaneelastomers (TPUs) combine high elongation and high tensile strength toform tough, albeit fairly high-modulus elastomers. Aromatic polyetherTPUs can have excellent flex life, tensile strength exceeding 5000 psi,and ultimate elongations greater than 700 percent. They are often usedfor continuously flexing, chronic implants such as ventricular-assistdevices, intraaortic balloons, and artificial heart components. TPUs caneasily be processed by melting or dissolving the polymer to fabricate itinto useful shapes.

The prospect of combining the biocompatibility and biostability ofconventional silicone elastomers with the processability and toughnessof TPUs is an attractive approach to what would appear to be a nearlyideal biomaterial. For instance, it has been reported that silicone actssynergistically with both polycarbonate- and polyether-basedpolyurethanes to improve in vivo and in vitro stability. Inpolycarbonate-based polyurethanes, silicone copolymerization has beenshown to reduce hydrolytic degradation of the carbonate linkage, whereasin polyether urethanes, the covalently bonded silicone seems to protectthe polyether soft segment from oxidative degradation in vivo.

PTG synthesized and patented silicone-polyurethane copolymers bycombining two previously reported methods: copolymerization of silicone(PSX) together with organic (non-silicone) soft segments into thepolymer backbone, and the use of surface-modifying end groups toterminate the copolymer chains. Proprietary synthesis methods makehigh-volume manufacturing possible.

PurSil™ silicone-polyether-urethane and CarboSil™silicone-polycarbonate-urethane are true thermoplastic copolymerscontaining silicone in the soft segment. These high-strengththermoplastic elastomers are prepared through a multi-step bulksynthesis where polydimethylsiloxane (PSX) is incorporated into thepolymer soft segment with polytetramethyleneoxide (PTMO) (PurSil) or analiphatic, hydroxyl-terminated polycarbonate (CarboSil). The hardsegment consists of an aromatic diisocyanate, MDI, with a low molecularweight glycol chain extender. The copolymer chains are then terminatedwith silicone (or other) Surface-Modifying End Groups™. We also offeraliphatic (AL) versions of these materials, with a hard segmentsynthesized from an aliphatic diisocyanate.

Many of these silicone urethanes demonstrate previously unavailablecombinations of physical properties. For example, aromatic siliconepolyetherurethanes have a higher modulus at a given shore hardness thanconventional polyether urethanes—the higher the silicone content, thehigher the modulus (see PurSil Properties). Conversely, the aliphaticsilicone polyetherurethanes have a very low modulus and a high ultimateelongation typical of silicone homopolymers or even natural rubber (seePurSil AL Properties). This makes them very attractive ashigh-performance substitutes for conventional cross-linked siliconerubber. In both the PTMO and PC families, certain polymers have tensilestrengths three to five times higher than conventional siliconebiomaterials.

Surface Modifying End Groups™ (SMEs) are surface-active oligomerscovalently bonded to the base polymer during synthesis. SMEs—whichinclude silicone (S), sulfonate (SO), fluorocarbon (F), polyethyleneoxide (P), and hydrocarbon (H) groups-control surface chemistry withoutcompromising the bulk properties of the polymer. The result is keysurface properties, such as thromboresistance, biostability, andabrasion resistance, are permanently enhanced without additionalpost-fabrication treatments or topical coatings. This patentedtechnology is applicable to a wide range of PTG's polymers.

SMEs provide a series of (biomedical) base polymers that can achieve adesired surface chemistry without the use of additives. Polyurethanesprepared according to PTG's development process couple endgroups to thebackbone polymer during synthesis via a terminal isocyanate group, not ahard segment. The added mobility of endgroups relative to the backboneis thought to facilitate the formation of uniform overlayersby thesurface-active (end) blocks. The use of the surface active endgroupsleaves the original polymer backbone intact so the polymer retainsstrength and processability. The fact that essentially all polymerchains carry the surface-modifying moiety eliminates many of thepotential problems associated with additives.

The SME approach also allows the incorporation of mixed endgroups into asingle polymer. For example, the combination of hydrophobic andhydrophilic endgroups gives the polymer amphipathic characteristics inwhich the hydrophobic versus hydrophilic balance may be easilycontrolled.

The following Materials are manufactured by CARDIOTECH CTE:

CHRONOFLEX®: Biodurable Polyurethane Elastomers are polycarbonatearomatic polyurethanes.

The ChronoFlex® family of medical-grade segmented polyurethaneelastomers have been specifically developed by CardioTech Internationalto overcome the in vivo formation of stress-induced microfissures.

HYDROTHANE™: Hydrophilic Thermoplastic Polyurethanes

HydroThane™ is a family of super-adsorbent, thermoplastic, polyurethanehydrogels, ranging in water content from 5 to 25% by weight, HydroThane™is offered as a clear resin in durometer hardness of 80A and 93 Shore A.

The outstanding characteristic of this family of materials is theability to rapidly absorb water, high tensile strength, and highelongation. The result is a polymer having some lubriciouscharacteristics, as well as being inherently bacterial resistant due totheir exceptionally high water content at the surface.

HydroThane™ hydrophilic polyurethane resins are thermoplastic hydrogels,and can be extruded or molded by conventional means. Traditionalhydrogels on the other hand are thermosets and difficult to process.

The following materials are manufactured by THERMEDICS:

Tecothane® (aromatic polyether-based polyurethane), Carbothane®(aliphatic polycarbonate-based polyurethane), Tecophilic® (high moistureabsorption aliphatic polyether-based polyurethane) and Tecoplast®(aromatic polyether-based polyurethane).

Polyurethanes are designated aromatic or aliphatic on the basis of thechemical nature of the diisocyanate component in their formulation.Tecoflex, Tecophilic and Carbothane resins are manufactured using thealiphatic compound, hydrogenated methylene diisocyanate (HMDI).Tecothane and Tecoplast resins use the aromatic compound methylenediisocyanate (MDI). AU the formulations, with the exception ofCarbothane, are formulated using polytetramethylene ether glycol (PTMEG)and 1,4 butanediol chain extender. Carbothane is specifically formulatedwith a polycarbonate diol (PCDO).

These represent the major chemical composition differences among thevarious families. Aromatic and aliphatic polyurethanes share similarproperties that make them outstanding materials for use in medicaldevices. In general, there is not much difference between medical gradealiphatic and aromatic polyurethanes with regard to the followingchemical, mechanical and biological properties:

-   -   High tensile strength (4,000 10,000 psi)    -   High ultimate elongation (250 700%)    -   Wide range of durometer (72 Shore A to 84 Shore D)    -   Good biocompatibility    -   High abrasion resistance    -   Good hydrolytic stability    -   Can be sterilized with ethylene oxide and gamma irradiation    -   Retention of elastomeric properties at low temperature    -   Good melt processing characteristics for extrusion, injection        molding, etc.

With such an impressive array of desirable features, it is no wonderthat both aliphatic and aromatic polyurethanes have become increasinglythe material of choice in the design of medical grade components. Thereare, however, distinct differences between these two families ofpolyurethane that could dictate the selection of one over the other fora particular application:

Yellowing

In their natural states, both aromatic and aliphatic polyurethanes areclear to very light yellow in color. Aromatics, however, can turn darkyellow to amber as a result of melt processing or sterilization, or evenwith age. Although the primary objection to the discoloration ofaromatic clear tubing or injection molded parts is aesthetic, theyellowing, which is caused by the formation of a chromophore in the MDIportion of the polymer, does not appear to affect other physicalproperties of the material. Radiopaque grades of Tecothane also exhibitsome discoloration during melt processing or sterilization. However,both standard and custom compounded radiopaque grades of Tecothane havebeen specifically formulated to minimize this discoloration

Solvent Resistance

Aromatic polyurethanes exhibit better resistance to organic solvents andoils than do aliphatics—especially as compared with low durometer (80 85Shore A) aliphatics, where prolonged contact can lead to swelling of thepolymer and short-term contact can lead to surface tackiness. Whilethese effects become less noticeable at higher durometers, aromaticsexhibit little or no sensitivity upon exposure to the common organicsolvents used in the health care industry.

Softening at Body Temperature

Both aliphatic and aromatic polyether-based polyurethanes softenconsiderably within minutes of insertion in the body. Many devicemanufacturers promote this feature of their urethane products because ofpatient comfort advantage as well as the reduced risk of vasculartrauma. However, this softening effect is less pronounced with aromaticresins than with aliphatic resins.

Melt Processing Temperatures

Tecothane, Tecoplast and Carbothane melt at temperatures considerablyhigher than Tecoflex and Tecophilic. Therefore, processing by eitherextrusion or injection molding puts more heat history into productsmanufactured from Tecothane, Tecoplast and Carbothane. For example,Tecoflex EG-80A and EG-60D resins mold at nozzle temperatures ofapproximately 310° F. and 340° F. respectively.

Tecothane and Carbothane products of equivalent durometers mold atnozzle temperatures in the range of 380° F. to 435° F.

Tecoflex®

A family of aliphatic, polyether-based TPU's. These resins are easy toprocess and do not yellow upon aging. Solution grade versions arecandidates to replace latex.

Tecothane®

A family of aromatic, polyether-based TPUs available over a wide rangeof durometers, colors, and radiopacifiers. One can expect Tecothaneresins to exhibit improved solvent resistance and biostability whencompared with Tecoflex resins of equal durometers.

Carbothane®

A family of aliphatic, polycarbonate-based TPUs available over a widerange of durometers, colors, and radiopacifiers. This type of TPU hasbeen reported to exhibit excellent oxidative stability, a property whichmay equate to excellent long-term biostability. This family, likeTecoflex, is easy to process and does not yellow upon aging.

Tecophilic®

A family of aliphatic, polyether-based TPU's which have been speciallyformulated to absorb equilibrium water contents of up to 150% of theweight of dry resin.

Tecogel, a new member to the Tecophilic family, is a hydrogel that canbe formulated to absorb equilibrium water contents between 500% and2000% of the weight of dry resin. The materials were designed as acoating cast from an ethanol/water solvent system.

Tecoplast®

A family of aromatic, polyether-based TPUs formulated to produce ruggedinjection molded components exhibiting high durometers and heatdeflection temperatures.

Four families of polyurethanes, named Elast-Eon™, are available fromAorTech Biomaterials.

Elast-Eon™ 1, a Polyhexamethylene oxide (PHMO), aromatic polyurethane,is an improvement on conventional polyurethane in that it has a reducednumber of the susceptible chemical groups. Elast-Eon™ 2, a Siloxanebased macrodiol, aromatic polyurethane, incorporates siloxane into thesoft segment Elast-Eon™ 3, a Siloxane based macrodiol, modified hardsegment, aromatic polyurethane, is a variation of Elast-Eon™ 2 withfurther enhanced flexibility due to incorporation of siloxane into thehard segment. Elast-Eon™ 4 is a modified aromatic hard segmentpolyurethane.

The following materials are manufactured by Bayer Corporation:

Texin 4210—Thermoplastic polyurethane/polycarbonate blend for injectionmolding and extrusion.

Texin 4215—Thermoplastic polyurethane/polycarbonate blend for injectionmolding and extrusion.

Texin 5250—Aromatic polyether-based medical grade with a Shore Dhardness of approximately 50 for injection molding and extrusion.Complies with 21 CFR 177.1680 and 177.2600.

Texin 5286—Aromatic polyether-based medical grade with Shore A hardnessof approximately 86 for injection molding or extrusion. Complies with 21CFR 177.1680 and 177.2600.

Texin 5290—Aromatic polyether-based medical grade with a Shore Ahardness of approximately 90. Complies with 21 CFR 177.1680 and177.2600.

It is appreciated that the devices described hereinabove, whilepreferably formed by injection molding of polyurethane, may also beformed by any suitable manufacturing method and may be formed of anysuitable medical grade elastomers. It is further appreciated that any ofthe following manufacturing methods may be utilized: injection moldingincluding inserting inserts, compression molding including insertinginserts, injection—compression molding including inserting inserts,compression molding of prefabricated elements pre-formed by any of theabove methods including inserting inserts, spraying including insertinginserts, dipping including inserting inserts, machining from stock orrods, machining from pre-fab elements including inserting inserts.

It is appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and subcombinations of various featuresdescribed hereinabove as well as variations and modifications theretowhich would occur to a person of skill in the art upon reading the abovedescription and which are not in the prior art.

It is appreciated that even though the illustrated embodimentshereinabove show specific prosthetic devices, the provision ofconfiguration patterns described herein may also be applied to anyprosthesis that includes a bone engagement surface.

It is a particular feature of preferred embodiments of the prosthesesdescribed hereinabove that the combination of their configuration withthe mechanical properties of the pliable material from which they areformed promotes bone growth and bone remodeling, enhancing anchoring andadhesion of the prostheses to the bone. The mechanical properties of thepliable material are characterized by a non-linear stress strainrelationship, such that when one region of the prosthesis is subject toloading, the prosthesis deforms in one or more regions, includingregions not directly adjacent to the region subject to the loading.These deformations are associated with the fluid-like quality of thepliable material and are not found in rigid materials. The loading andthe deformations within the prosthesis cause pressure exerted by theprosthesis onto the adjacent bone to be distributed in a manner similarto hydrostatic pressure generated by pressurized fluid within acontainer.

This results in the creation of strain fields in the bone adjacent tothe prosthesis with strain magnitudes comparable to those found in bonesof a physically active person. It is this strain field, which is createdin substantial portions of the bone, that activates bone growth and boneremodeling simulating natural bone growth and remodeling.

The bone remodeling process, associated with preferred embodiments ofthe prostheses of the present invention, may be a continuous processthroughout the life of the prostheses. As described hereinabove, themigration of bone cells into the channels or recesses proceeds graduallyover time. As new bone cells fill in the voids defined between therecessed area of the prosthesis and the bone surface, new areas ofcontact are created between bone and the walls of the recessed area.These new contact areas are operative to participate regionally in theremodeling process described hereinabove.

The remodeling process contributes to the strengthening of the entirebone, including the new bone formed within the recessed areas. Evenafter the new bone cells fill the entire recess, the process of boneremodeling may continue through the entire bone contact surface.

It is appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and subcombinations of various featuresdescribed hereinabove as well as variations and modifications theretowhich would occur to a person of skill in the art upon reading the abovedescription and which are not in the prior art.

1. An implantable artificial joint prosthesis comprising: at least onejoint defining element defining a bone-engaging surface, saidbone-engaging surface including an anchoring mechanism operative forenhancing anchoring and adhesion of the joint defining element to thebone to enhance the stability and longevity of the prosthesis withoutthe use of cement, wherein said bone-engaging surface is configured witha hexagonal configuration pattern, said hexagonal configuration patterndefined by a plurality of protruding hexagonal contact surface portionssized and shaped for direct contact with bone, each surrounded by aperipheral channel.
 2. An implantable artificial joint prosthesisaccording to claim 1 and wherein said at least one joint definingelement is formed of a material having mechanical properties which arecharacterized by a nonlinear stress strain relationship.
 3. Animplantable artificial joint prosthesis according to claim 1 and whereinsaid at least one joint defining element defines a generallyhemispherical convex bone-engaging surface.
 4. An implantable artificialjoint prosthesis according to claim 3 and wherein said at least one boneengagement surface has formed thereon a generally annular outwardlyextending protrusion.
 5. An implantable artificial joint prosthesisaccording to claim 4 and wherein said protrusion defines a generallyannular undercut.
 6. An implantable artificial joint prosthesisaccording to any of the preceding claims and wherein said at least onebone-engaging surface is arranged for snap fit engagement with a bone.7. An implantable artificial joint prosthesis according to any of claims1, 2, 3, 4, or 5, wherein said at least one bone-engaging surface isarranged for press fit engagement with a bone.
 8. An implantableartificial joint prosthesis according to claim 1 and wherein saidchannels are each defined by wall surfaces and a bottom surface.
 9. Animplantable artificial joint prosthesis according to claim 1 and whereinsaid channels are defined to provide an undercut engagement portion. 10.An implantable artificial joint prosthesis according to claim 8 andwherein said channels are defined to provide an undercut engagementportion.
 11. An implantable artificial joint prosthesis according toclaim 10 and wherein said undercut engagement portion comprises arelatively wider cross sectional dimension near said bottom surface anda relatively narrower cross sectional dimension away from said bottomsurface.
 12. An implantable acetabular prosthesis comprising: anacetabular cup formed of a polymer having a non-linear stress-strainrelationship, the acetabular cup having an outer surface and an opposinginner surface, the outer surface including a bone-engaging portionhaving a partially hemispherical convex shape including a plurality ofrecessed channels oriented to define a plurality hexagonal contactsurfaces, the plurality of recessed channels having a dovetail shapedefined by a bottom surface and opposing side surfaces extending at anoblique angle with respect to the bottom surface such that the opposingside surfaces are separated by a first distance at a first positionadjacent the bottom surface and separated by a second distance, lessthan the first distance, at a second position spaced from the bottomsurface.
 13. The acetabular prosthesis of claim 12, wherein the outersurface further comprises an annular protrusion extending annularlyaround the outer surface of the acetabular cup between an apex of theacetabular cup and a rim of the acetabular cup.
 14. The acetabularprosthesis of claim 13, wherein the annular protrusion defines anannular undercut.
 15. The acetabular prosthesis of claim 14, wherein theannular protrusion is arranged for snap-fit engagement with a preparedportion of an acetabulum.
 16. The acetabular prosthesis of claim 15,wherein the annular protrusion bounds the bone-engaging portion of theouter surface.
 17. The acetabular prosthesis of claim 16, wherein thebone-engaging portion is positioned closer to the apex of the acetabularcup than the rim of the acetabular cup relative to the annularprotrusion.
 18. The acetabular prosthesis of claim 17, wherein theacetabular cup has a generally uniform thickness between the outersurface and the opposing inner surface.
 19. The acetabular prosthesis ofclaim 18, wherein the acetabular cup is formed of an injection moldedpolyurethane.
 20. An implantable acetabular cup comprising: a bodyformed of a flexible polymer having a non-linear stress-strainrelationship, the body having an outer surface and an opposing innersurface, the outer surface including a bone-engaging portion having apartially hemispherical convex shape including a plurality of bonecontact portions bounded by a plurality of recessed channels, theplurality of recessed channels having a dovetail cross-section generallydefined by a bottom surface and opposing side surfaces extending at anoblique angle with respect to the bottom surface such that the opposingside surfaces are separated by a first distance adjacent the bottomsurface and are separated by a second distance, less than the firstdistance, adjacent the bone contact portions, wherein the body isconfigured for implantation into a prepared acetabulum without the useof cement such that at least the bone contact portions of the bodydirectly contact the prepared acetabulum.
 21. The implantable acetabularcup of claim 20, wherein the plurality of bone contact portions have ageometrical profile.
 22. The implantable acetabular cup of claim 21,wherein the plurality of bone contact portions have a generallyhexagonal profile.
 23. The implantable acetabular cup of claim 20,wherein the outer surface further comprises an annular protrusionextending annularly around the outer surface of the body between an apexof the body and a rim of the body.
 24. The acetabular prosthesis ofclaim 23, wherein the annular protrusion defines an annular undercut.25. The acetabular prosthesis of claim 24, wherein the annularprotrusion is arranged for snap-fit engagement with a prepared portionof an acetabulum.
 26. The acetabular prosthesis of claim 25, wherein theannular protrusion bounds the bone-engaging portion of the outersurface.
 27. The acetabular prosthesis of claim 26, wherein thebone-engaging portion is positioned closer to the apex of the acetabularcup than the rim of the acetabular cup relative to the annularprotrusion.
 28. An implantable acetabular cup comprising: a body formedof a flexible polymer having a non-linear stress-strain relationship,the body having an outer surface and an opposing inner surface, theouter surface including a bone-engaging portion having a partiallyhemispherical convex shape including a plurality of bone contactportions bounded by a plurality of recessed channels, the plurality ofrecessed channels having a dovetail cross-section generally defined by abottom surface and opposing side surfaces extending at an oblique anglewith respect to the bottom surface such that the opposing side surfacesare separated by a first distance adjacent the bottom surface and areseparated by a second distance, less than the first distance, adjacentthe bone contact portions; wherein at least the bone-engaging portion ofthe outer surface includes a bioactive coating.
 29. The implantableacetabular cup of claim 28, wherein the bioactive coating comprises anelastomer.